Chapter 40

[650]See Rep. Brit. Assoc. 1841, pp. 137-142.

Length of the Iguanodon.—The length of the united head and trunk, according to my estimate inGeol. S. E.p. 316, is seventeen feet and a half; by Professor Owen’s estimate it is reduced to fifteen feet;[651]a difference of noimportance in such merely approximative calculations, particularly when the form of the cranium is unknown.[652]

[651]Ibid. p. 144.[652]The more recently discovered specimen of lower-jaw, already referred to, page 693, indicates a length of between three and four feet for the entire jaw,Petrif.p. 249.

[651]Ibid. p. 144.

[652]The more recently discovered specimen of lower-jaw, already referred to, page 693, indicates a length of between three and four feet for the entire jaw,Petrif.p. 249.

Lign. 226. Bones of the Feet and Claws of the Iguanodon.Wealden.Tilgate Forest.(SeeWond.pl. in.)Fig.1.—Metatarsal: original 6 inches long: upper surface.2.—Metacarpal bone.3.—Under surface of fig. 1.4.—A phalangeal bone of the fore-foot: the original 14 inches long.4a.—A transverse section of the same, showing the medullary cavity.5.—One of the second row of phalangeal bones of the fore-foot.6.—View from above of one of the claw-bones of the hind-foot;1/6nat.7.—Profile of claw-bone of fore-foot:[653]1/6nat.8.—Metatarsal, or bone of the hind-foot:1/8nat.a.Denotes the proximal articulation, or that nearest the trunk.b.The distal, or extremity most distant from the trunk.

[653]This bone is conjecturally referred by Prof. Owen to the Megalosaurus.

The estimated extent of the tail has been subject to variation. My early estimate of its length gave rise to theidea of this reptile having attained seventy feet in length. Professor Owen, however, considered that the abbreviated character of the anterior caudal vertebræ indicated a far less extent of tail, which the Professor estimated at thirteen feet; this opinion, from the evidence then before us, seemed well founded, but from evidence since afforded by a series of eleven caudal vertebra, belonging to the middle region of the tail, that have been lately discovered, (Petrif.p. 312,) it is not at all improbable, that, instead of all the caudal vertebræ being abbreviated, these elements of the tail were elongated as in the corresponding part of the skeleton of the Iguana, and that the largest Iguanodons may have attained a length of from sixty to seventy feet.

The author’s physiological inferences as to the structure and economy of the Iguanodon, deduced from the study of the osseous remains of this singular creature, especially the lately discovered remains of the jaw-bones, are given in full at pp. 307-313Petrif.orFoss. Brit. Mus.: and at pp. 335-338,ibid.may be found some general remarks on the physical geography and the nature of the fauna and flora of the country inhabited by these stupendous reptiles, whose remains are so characteristic of the Wealden rocks.

Jaw of the Regnosaurus.(Petrif.p. 333.)—A portion of the right ramus, or side, of the lower jaw of this reptile was discovered in a block of sandstone from Tilgate Forest. It consists of a fragment, six inches long, of the dentary bones, with a small portion of the opercular; and it contains the fangs of fifteen teeth, which are closely and evenly set in a regular series, and imbedded laterally in grooves, or sockets, in the dentary bone; there are three or four sockets of successional teeth on the inner side of the bases of the old teeth. (Phil. Trans.1841, pl. v. figs. 1, 2.) Unfortunately, all the crowns of the teeth are wanting. The outer parapet of the dentary piece is entire, and itsupper margin is finely crenated. All the fangs of the teeth are exposed, but there are traces of a thin inner wall, indicating the probability that, as in the Megalosaurus, the teeth were supported medially by an osseous plate, and were implanted in distinct sockets.[654]In my memoir on this fossil jaw in thePhil. Trans.(1841, p. 131), I referred it to the genus Iguanodon; but subsequent observations have led me to conclude that it is generically distinct; and in my Memoir on the Jaw of the Iguanodon, inPhil. Trans.1848 (p. 183), I have proposed for the animal to which it belonged the distinct generic appellation,Regnosaurus, with the specific nameNorthamptoni.

[654]The collector will perceive the importance that attaches to the discovery of even a fragment of the jaw of an unknown reptile, containing teeth in their natural position.

LACERTIAN REPTILES.

IV. Lacertian Reptiles.—The recent Lacertians, or true Lizards, are smaller and less highly organized reptiles than the Saurians of the Crocodilian order; and their dermal covering consists of a finer and more delicate squamous integument. They are also characterized by important modification in their osteological structure. The spinal column is almost always composed of concavo-convex vertebræ, with the convexity behind; the ribs are slender and rounded, having a single convex tubercle of attachment. The fossil species are, for the most part, of gigantic dimensions, and deviate in a striking manner from any that now exist. Vertebræ of the recent lacertian type are very rare in the secondary strata; I believe a few in my cabinet, obtained from the sandstone of Tilgate Forest, and which belonged to a very small unknown reptile, are the most ancient examples at present known.

Lign. 227. Mosasaurus Hoffmanni.(The original is feet by 21/2feet.)Remains of the jaws of the great fossil reptile of Maestricht.

Mosasaurus.Bd.pl. xx.;Wond.p. 311;Petrif.p. 193.—Of the fossil lizard of Maestricht, namedMosasaurus(lizard of the Meuse) from the river adjacent to the quarries of St. Peter’s Mountain, in which its remains have been discovered, I have given a detailed account at pages 193-196 ofPetrif.A specimen, with the jaws, and bones of the palate armed with teeth, now in the museum at Paris, has long been celebrated, and is still the most precious relic of this extinct reptile hitherto discovered; a reduced representation is given inLign.227; andPict. Atlas, pl. lxx. This is theMosasaurus Hoffmanni.[655]The specimen is four and a half feet long, and two and a half feet wide; it consists of both sides of the lower jaw, with the right ramus of the upper jaw in its natural position, and the left, which is displaced, lying across the articular extremity of the left branch of the lower jaw: of the pterygoid bones, which are armed with teeth; of the left tympanic bone (os quadratum),which is but little removed from its natural situation, and connects the lower jaw with the cranium; one of the metacarpal or metatarsal bones, and some fragments.[656]

[655]Several fine portions of the jaws, and many vertebræ of this animal, are in the British Museum: seeFoss. Brit. Mus.p. 139. In a splendid work,Histoire Naturelle de la Montagne de St. Pierre, by the late Faujas St. Fond (1 vol. folio, with numerous plates), there are admirable figures of the remains of the Mosasaurus.[656]In the British Museum there is a cast of this specimen, in a case near the bones of the Iguanodon.

[656]In the British Museum there is a cast of this specimen, in a case near the bones of the Iguanodon.

Lign. 228. Mosasauroid Teeth.[657]1/2nat. size.Figs.1a,2a. Transverse sections of the crowns of the teeth, figs. 1 and 2 respectively.

[657]Reduced from figures accompanying Dr. Gibbes’s Memoir "On the Mosasaurus and three allied new genera," (with plates,) in theSmithsonian Contributions, vol. ii. 1849. This interesting paper comprises much information regarding the Mosasaurians of the Cretaceous deposits of N. America; but we cannot fully coincide with the author in his palæontological determinations.

The teeth are large, and supported on expanded conical osseous eminences, which are anchylosed to the alveolar ridge of the jaw (acrodont). The crown of the tooth is conical and recurved, with the outer face nearly flat, and this space is bordered on each side by a longitudinal ridge; giving the tooth somewhat of a pyramidal figure. (SeeLigns.228-230.) Professor Owen states that the crown consists of a body of simple and firm dentine, with fine and close-set calcigerous tubes, enclosing a simple pulp-cavity; irregular processes of the latter extend as medullary canals into the conical base of the tooth, but not, as in the Iguanodon, into the substance of the coronal dentine; the dentine is invested with a moderately thick coat of enamel.[658]

[658]See Odontography, p. 258, and pl. lxxii.; the student should also consult Cyclop. Anat. Phys.Art.Teeth.

The vertebræ of the Mosasaur, as is usual in the existing lizards and crocodiles, are concave in front and convex behind, and the neural arch is united to the centrum by suture. The entire vertebral column ofM. Hoffmanniappears to have consisted of 131 vertebræ, of which 97 belonged to the tail.[659]This Mosasaur was about twenty-five feet long.

[659]See Cuvier,Oss. Foss.vol. v. pp. 326-334.

Lign. 229. Tooth of Mosasaurus:magn. twice.Either a pterygoid tooth of M. Hoffmanni, or a jaw-tooth of M. gracilis.Chalk.Gravesend.(In Mr. Wetherell’s Collection.)

This extinct lacertian reptile forms an intermediate link between the Saurians without pterygoid teeth (Monitors) and those with them (Iguanas). Its crocodilian affinities are but partial.

The Mosasaurus appears to have had webbed feet, adapted or crawling on land as well as for swimming,[660]and a long and vertically expanded tail, serving as a powerful oar, and enabling the animal to stem the roughest waters.

[660]See Prof. Owen’s observations on the bones that have been regarded as referable to the extremities of this creature, and especially on the phalangeal and other bones of the Mosasaur of the New Jersey greensand;Monog. Cret. Rept.1851, pp. 36-40.

Prof. Goldfuss has described the remains of another and smaller species of Mosasaurus (M. Maximiliani), fromUpper Missouri, U.S.; and Prof. Owen, in Dixon's "Fossils of Sussex," has established a third and still smaller species (M. gracilis),[661]to which he refers the four or five mosasaurian vertebræ found in the Chalk of Sussex. Two of these (caudal) are figured inGeol. S. E.p. 146, andPetrif.Lign.44; and these and others are lithographed in plate viii. of Prof. Owen’sMonog. Cret. Reptilia, 1851.

[661]See alsoMonograph on the Reptiles of the Chalk, 1851, p. 31, and plate ix.

The remains of Mosasaurus occur also in the cretaceous sands of New Jersey, U. S. (See Dr. Morton’sSynopsis of the Organic Remains of the United States, 1834; and the Quart. Journ. of the Geological Society, vol. v. 1849.)

Leiodon anceps.[662]—Under this name Professor Owen has described a splendid fossil, consisting of a portion of the lower jaw of an acrodont reptile, with teeth, obtained by Edward Charlesworth, Esq. from the Chalk north of the Thames. This specimen was submitted to my inspection, many years since, by Mr. Charlesworth, and I then pointed out the analogy of this acrodont jaw to that of the Mosasaurus.

[662]Ibid. p. 42, pl. ix. A.

Prof. Owen in 1840 (Odontog.p. 261), and in 1841 (Rep. Brit. Assoc.p. 144), described and figured some teeth from the same specimen, which were lent by Mr. Charlesworth. These teeth the Hunterian Professor regarded as characteristic of a new genus of Mosasauroid reptile, to which he gave the nameLeiodon(in allusion to the smoothness of the teeth). In 1845 (Rep. Brit. Assoc.p. 60) Mr. Charlesworth noticed, and in 1846 (London Geol. Journal, p. 23, plates iv. and vi.) figured and described, the above mentioned portion of jaw with teeth, under the nameMosasaurus stenodon; and in 1851 Prof. Owen figured and described this specimen under the name ofLeiodon anceps, which was originally proposed for the animal, as known from its teeth, in 1840.

The portion of bone on which the teeth, five in number are implanted is seven inches in length, and is, in Professor Owen s opinion, the dentary piece of the lower jaw, and not a portion of a pterygoid bone. Mr. Charlesworth has had a section made of four of the teeth, and finds that the pulp-cavities are more or less occupied with solid cones of silex, which must have permeated the osseous parietes of the teeth.

Lign. 230. Mosasauroid Tooth.Resembling the back-teeth in the lower jaw of Mosasaurus Hoffmanni.Chalk.Gravesend.(In the Collection of Mr. Wetherell.)

The teeth of Leiodon have a simple pulp-cavity, surrounded by fine dentine, with an external layer of smooth enamel. The apex of the crown is sharp-pointed; the body of the crown is slightly recurved; its base is expanded into a thick circular fang, which is anchylosed to a short conical process of the alveolar border of the jaw: the teeth differ from those of the Mosasaurus in having the outer side as convex as the inner side, the transverse section being an ellipse with pointed ends, which latter correspond with the lateral trenchant edges of the crown of the tooth: the teeth are more closely set than in the Mosasaur and Geosaur. (Owen.)

Geosaurus Sœmmeringii.Petrif.p. 175.—In the British Museum are the remains of a reptile from the "white Jura" (upper oolite) of Monheim, in Franconia, which Cuvier describes as being more nearly related to the Lizards than Crocodiles. The length of this reptile is estimated at about ten feet. The eyes had a circle of osseous plates in thesclerotica, like those of the Ichthyosaurus; the teeth resemble those of the Mosasaurus in being sub-compressed and recurved, but they are at once distinguished by their anterior and posterior finely serrated sharp edges; the crown is invested with an external coat of enamel.[663]

[663]Oss. Foss. tom. v. p. 343.

Raphiosaurus subulidens.—A portion of a lower jaw, containing twenty-two closely set, subulate teeth, anchylosed by their bases to a shallow alveolar groove and an outer alveolar parapet of bone, as in the Iguana, thus corresponding with the pleurodont Lizards, is described under this name by Professor Owen, (Geol. Trans.2d ser. vol. vi. pl. xxxix.); andMonog. Cret. Rept.(Pal. Soc.) 1851, p. 19, pl. x. figs. 5, 6. It is from the Lower Chalk, near Cambridge, and is in the collection of James Carter, Esq. of that place. Remains of Raphiosaurus have been found also in the Chalk at Northfleet, Kent.

Dolichosaurus longicollis.—In the Chalk of Kent was found, some years since, a considerable portion of the skeleton of a lacertian reptile, consisting of the posterior half of the spinal column, with remains of the pelvic and thigh bones; it was figured in theGeol. Trans.2d ser. vol. vi. pl. xxxix.; and is now in the collection of Sir P. G. Egerton. From the researches of the late Mr. Dixon, it appears that a mutilated reptilian head and anterior portion of a spinal column, with fore-arm and scapular bones, now in the collection of Mr. Smith, of Tunbridge Wells, belong to the same skeleton as the vertebral remains above mentioned. Both specimens were obtained at the same timefrom the well-known chalk-pit at Burham, Kent. Professor Owen has lately described these interesting remains in detail (Monog. Cret. Rept.1851, pp. 22, &c.), and finds no intrinsic contradiction to exist to the historical evidence adduced as to the probability of the two moieties having belonged to the same individual. In the two specimens there exist sixty-three concavo-convex (procœlian) vertebræ, of which fifty-seven form the series between the skull and the pelvis, giving the trunk a length of about eighteen inches. This unique reptile was elongate and snake-like in its form, with the abdomen deep and narrow, like that of the water-snakes: its limbs were short; its tail, from the character of the few caudal vertebræ remaining, must have been relatively long and powerful. This long and slender lacertian was therefore probably to a considerable degree aquatic in its habits, swimming with an undulatory eel-like movement.

The Dolichosaurus (long-lizard) presents somewhat of the ophidian character in the number and size of its cervical vertebræ, in the size and shape of its ribs, and in the slender proportions of its trunk and head; but, with these partial exceptions, its affinities are truly lacertian. (Owen.)

Rhynchosaurus articeps.Lign.231.—In a quarry of Upper New Red Sandstone at Grinsell, near Shrewsbury, Dr. O. Ward discovered a skull (31/2inches long), vertebræ, ribs, bones of the pectoral and pelvic arches, portions of two femora with medullary cavities, and fragments of other bones of a very remarkable lacertian reptile (Lign.231). The lower jaw is preserved with the skull in its natural position. The cranium in its general aspect resembles that of a turtle, rather than of a lizard; for the intermaxillary bones are double, as in Chelonians, and symmetrical, and are not united by a median process; they are very long, and curve downwards, giving the fore part of the skull the profile of a parrot. SeeLign.231.

Lign. 231. Rhynchosaurus articeps.New Red Sandstone; near ShrewsburyFig. 1.—Lateral view of the cranium and lower jaw:1/2nat size.Cranium.a, a.Intermaxillary bones.b.Nasal.c.Frontal.d.Maxillary.e.Anterior frontal.f.Lachrymal.g.Malar.h.Posterior frontal.i.Orbital division of posterior frontal.k.Temporal.l.Tympanic.Lower Jaw.m.Dentary.n.Coronoid.o.Articular.p.Angular.q.Opercular or splenial.r.The orbit.Fig. 2.—The upper aspect of a dorsal vertebra:nat. size.

Cranium.

Lower Jaw.

Fig. 2.—The upper aspect of a dorsal vertebra:nat. size.

There are no teeth apparent in either jaw: the margin of the upper maxillary has feeble dentations, but in the lower jaw even these indications are wanting, and it is probable that this reptile had its jaws encased by a bony or horny sheath, as in birds and turtles.[664](Owen.)

[664]Rep. Brit. Assoc. 1841, p. 150. See also Camb. Phil. Trans, vol. vii. p. 357, tab. 5, 6.

Thecodontosaurus and Palæosaurus.Ly.p. 306, figs. 348, 349.—Numerous bones and teeth of reptiles occur in the Magnesian Conglomerate, near Bristol, and have been described by Dr. Riley and Mr. Stutchbury in an interesting memoir to which reference should be made for details (Geol. Trans.2d ser. vol. v. p. 349, pl. xxix. xxx.). The bones denote an approach to the lizards; the teeth are implanted in sockets; these reptiles, therefore, belonged to the group termed thecodont, and the nameThecodontosaurus, given tothese extinct Saurians by Dr. Riley, has reference to this character. The teeth are pointed, compressed laterally, slightly convex on each side, with a trenchant, finely serrated edge in front and behind; the fang is sub-cylindrical. Other teeth from the same deposit, possessing the same general characters, but distinguished by peculiarities of form, have been referred to another genus, namedPalæosaurus. The vertebræ found associated with the teeth and jaws are biconcave, and are remarkably characterized by the great depth of the spinal canal in the middle of the centrum or body of the vertebræ, so that the spinal chord must have presented a moniliform or bead-like appearance. These reptiles, in theirthecodonttype of dentition, biconcave vertebræ, double-headed ribs, and proportionate size of the bones of the extremities, are nearly allied to theTeleosaurus, (seeante,p. 679); but they combine a lacertian form of tooth, and a lacertian structure of the pectoral, and probably of the pelvic arches, with these crocodilian characters; they have also distinctive modifications: such, for example, as the moniliform spinal chord.[665]

[665]Owen; Rep. Brit. Assoc. 1841, p. 155, &c.

Dicynodon.Ligns.232,233,234.—This singular fossil reptile was discovered, by Mr. Bain, in South Africa. It is distinguished, by some remarkable peculiarities of structure, from other animals of the Saurian order; of which it represents a new tribe, or sub-order. The cranium is narrow; the nostrils are divided, as in Lizards, and not confluent, as in Chelonia; the skull, in other respects, much resembles in general appearance that of a Turtle; the orbits are large; the jaws are edentulous, as in the Turtles, with the exception of a pair of long tusks,[666]implanted in sockets in the upper maxillary bone, like those of the Walrus; these tusks are of a finer texture than that of the Crocodile’s teeth, andalmost as dense as in the Hyæna. These creatures present in the most striking manner that blending of the peculiarities of several existing orders, which is continually presented to the palæontologist; for with a type essentially lacertian are combined crocodilian and chelonian modifications. Although no vestiges of these reptiles have been discovered in England or in Europe, yet the occurrence of an allied form, theRhynchosaurus(Lign.231), in our New Red Sandstone, and the probability that the South African reptiliferous deposits may, from their position, belong to the Triassic Epoch, induce me to give a somewhat extended notice of these extraordinary fossils: and I am led to do so on another account, namely, because the memoir,[667]of which the following is a brief abstract, is so excellent an example of the manner in which such investigations should be conducted, so as to arrive at any satisfactory conclusions as to the characters and relations of the lost types of beings, whose fragmentary and petrified relics are the only vestiges that remain.

[666]Hence the generic name,Dicynodon: from δις (twice), and κυνὁδονς (canine tooth).[667]Prof. Owen’s Memoir on the Dicynodon, Geol. Trans. 2d ser. vol. vii. pp. 59,et seq.; and plates iii. to vi.

[666]Hence the generic name,Dicynodon: from δις (twice), and κυνὁδονς (canine tooth).

[667]Prof. Owen’s Memoir on the Dicynodon, Geol. Trans. 2d ser. vol. vii. pp. 59,et seq.; and plates iii. to vi.

The fossils under consideration were exhumed some years since by Mr. Andrew Geddes Bain, from the intensely hard argillo-calcareous nodules of the sandstone strata which range over an immense tract of country beyond the mountains north of Capetown,[668]The extensive series of these and other fossils from South Africa, collected by the indefatigable labour of Mr. Bain, have lately been deposited in the British Museum; but the specimens described and figured in Prof. Owen’s Memoir, above alluded to, are nearly all that have as yet been successfully worked out from the exceedingly hard matrix in which the bones are imbedded. These consist of crania and jaws, referable to four species.[669]

[668]For a notice of the geological structure of this region, see Mr. Bain’s paper in Geol. Trans. 2d ser. vol. vii. pp. 53, &c.; and the abstract of a later Memoir by Mr. Bain, in the Literary Gazette, Dec. 18, 1852 (No. 1874).[669]Namely, Dicynodon lacerticeps (lizard-head), D. testudiceps (turtle-bead), and D. strigiceps (owl-head), the trivial names of which have reference to the general form of the head; and D. Bainii, the largest, but unfortunately as yet the least known species, which takes the name of the intelligent and energetic discoverer and collector of the whole.

[669]Namely, Dicynodon lacerticeps (lizard-head), D. testudiceps (turtle-bead), and D. strigiceps (owl-head), the trivial names of which have reference to the general form of the head; and D. Bainii, the largest, but unfortunately as yet the least known species, which takes the name of the intelligent and energetic discoverer and collector of the whole.

Lign. 232.

Lign. 233.

Lign. 232andLign. 233.Dicynodon lacerticeps.(Owen.)South Africa.(See Geol. Trans. 2d ser. vol. vii. pl. iii.)The letters of reference correspond in the two figures.Lign. 232.Side view of the Cranium and Lower Jaw:1/3nat. size.Lign. 233.Upper aspect of the Cranium:1/3nat. size.Cranium and Upper Jaw.a, a.Intermaxillary bone.b, b.Nasal.c, c.Frontal.d, d.Maxillary.e, e.Prefrontal.f, f.Lachrymal.g, g.Malar.h, h.Post-frontal.i, i.Parietal.k, k.Temporal.l, l.Tympanic.m, m.Mastoid.n, n.Nasal apertures.o, o.Orbits.oc, oc.Basi-occipital.t, t.Temporal fossæ.t′, t′.Canine teeth in the upper jaw.Lower Jaw.1.Dentary bone.2.Coronoid.3.Opercular.4.Angular.5.Articular.6.Surangular.

The most striking character in these crania is the presence of a pair of long, sharp-pointed, gently curved tusks, implanted in the superior maxillary bones, and which descend, one on each side of the fore-part of the lower jaw, as seen inLigns.232and233,t,t′. This is a dental character which, with this exception, is peculiar to the mammalia (the Walrus, Musk-deer, and Machairodus), and is rare even in that class.

Examination of the skull.—One of the crania showed the median undivided process of a singleintermaxillarybone, ascending and separatingtwo distinct anterior nasal apertures; in another, the boundaries of a very much contracted cranial cavity were evident: these characters combined to prove that the skulls were referable to air-breathing oviparous and cold-blooded animals, or Reptiles; but neither to Crocodilians nor Chelonians, and for the following reasons:—

1stly. The originals were not mammalians; for no mammalian has theintermaxillary bone single(as inLign.233,a), or theexternal bony nasal aperture double; and neither mammalian nor bird has the cavity for the brain so relatively small as in this fossil.

2dly. They were not Crocodiles; for in all crocodiles the intermaxillary bone is divided by a suture, and the anterior nasal aperture is single and on the median line, as in mammalia.

3dly. They were not Chelonians; for all turtles have thenasal opening single and placed in the middle of the fore-part of the skull, in the very situation which, in the Dicynodon, is occupied by the convex imperforate median plate of the broad intermaxillary bone.

4thly. They could not be Fishes, as those animals have no well-defined external respiratory nasal apertures.

5thly. They were neither Batrachians (frogs) nor Ophidians (serpents); for, although the reptiles of these two orders have a single intermaxillary and double nostrils, like the fossils, the latter are at once separated from them by the presence of a strong and complete zygomatic arch (Ligns.232and233,g,d), continued from the tympanic bone to the large immovably articulated superior maxillary.

Lastly, the characters last named, and the presence of vertical tympanic pedicles (Lign.232,l), suspended by their upper part to the junction of the zygomatic and mastoid bones, prove the affinity to the lacertians or true lizards.

These bidental crania have certain characters in common with that of the Rhynchosaur, which is also, as we have before seen, of the true lacertian group, but the Dicynodonts are more nearly allied to the Crocodiles and the Chelonians than the Rhynchosaurus appears to be.

Referring to the original Memoir for anatomical details, I must limit this notice to a few additional general remarks. Both the jaws are edentulous, with the exception of the pair of tusks, as in Chelonians; there are no traces of teeth, or of their sockets, in the lower jaw, which is short and very deep, and anchylosed at the symphysis, as in turtles; the alveolar border forms a smooth trenchant edge, which shuts within the corresponding part of the upper jaw: it is probable that both jaws were covered by horn, as in the chelonians. The tusks are implanted in wide and deep conical alveoli in the suborbital part of the maxillary bone, and project about two inches beyond the sockets (Lign.232); they are long and pointed, and are directed downwards and forwards, with aslight backward curve, and slightly converge towards their extreme points (Lign.233). These teeth consist of a simple body of unvascular dentine, with a very thin external coat of enamel. The tooth-ivory is more dense than in any known reptile, and approaches in its intimate texture that of the canines of the carnivorous mammals. The base of the tooth has a conical cavity (Lign.234), indicating a persistent matrix or dental pulp, the rest of the tooth without the socket being solid. There are no traces whatever of the germs of successional teeth. It is therefore inferred, that, like the tusks and scalpriform incisors of mammalia, the canine or maxillary teeth of the Dicynodon were capable of constant growth and renovation; thus offering an approach to the typical dentition of mammalia, unknown in any other reptiles.

As the points of the teeth in the only known perfect specimen are unworn, it is inferred that these tusks were not employed either as instruments for obtaining food, as in the Dugong, or for locomotion, as in the Walrus, but were simply offensive and defensive weapons.[670]

[670]See Prof. Owen’s detailed account of these curious dental organs in the Memoir already referred to, and in theArt.Teeth, in the Cyclopædia of Anatomy and Physiology.

Lign. 234.Dicynodon testudiceps.(Owen.)(Geol. Trans. 2d ser. vol. vii. pl. v. figs. 3 & 4.)Fig.1.—Longitudinal section of the fang of the tooth implanted in its socket:1/3nat. size.1a.—Transverse section of the tooth.

A few sub-biconcave vertebræ and other undetermined bones were associated with these remains; and many similar crania, both with and without the tusks, and other cranial remains with jaws armed with numerous teeth, as well asindications of smaller reptiles, form part of Mr. Bain’s collections now in the National Museum, awaiting the skilful manipulation of the experienced workman to clear away their hard investing matrix, and the scientific examination of the palæontologist to elucidate their zoological characters.

Telerpeton Elginense (Mantell).Ligns.235and236.—This is the oldest Reptile yet known.[671]Its remains consist of the impression[672]of a skeleton of a small, four-footed, vertebrate animal, on a block of the Old Red or Devonian Sandstone from Spynie, near Elgin, North Britain. It was obtained by Mr. Patrick Duff, in 1851; and a detailed description of this unique fossil, with an illustrative plate, will be found in the Quarterly Journal of the Geological Society, vol. viii. pp. 100,et seq.; together with a notice by Captain Brickenden of the geology of the district where the specimen was found, and a paper on some fossil foot-prints,[673]discovered by this geologist in the same rock.

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