General Remarks on the Distribution of the Lacertilia.
The distribution of the Lacertilia is, in many particulars, strikingly opposed to that of the Ophidia. The Oriental, instead of being the richest is one of the poorest regions, both in the number of families and in the number of peculiar genera it contains; while in both these respects the Neotropical is by far the richest. The distribution of the families is as follows:—
The Nearctic region has 7 families, none of which are peculiar to it; but it has 3 peculiar genera—Chirotes,Ophisaurus, andPhrynosoma.
The Palæarctic region has 12 families, with two (Ophiomoridæ and Trogonophidæ, each consisting of a single species) peculiar; while it has 6 peculiar or very characteristic genera,Trogonophisin North Africa,Psammodromusin South Europe,Hyalosaurusin North Africa,Scincusin North Africa and Arabia,Ophiomorusin East Europe and North Africa, andPhrynocephalusin Siberia, Tartary, and Afghanistan. We have here a striking amount of diversity between the Nearctic and Palæarctic regions with hardly a single point of resemblance.
The Ethiopian region has 13 families, only one of which (the Chamæsauridæ, consisting of a single species) is altogether peculiar; but it possesses 21 peculiar or characteristic genera, 9 belonging to the Zonuridæ, 2 to the Sepidæ, 7 to the Geckotidæ, and 3 to the Agamidæ.
The Oriental region has only 8 families, none of which are peculiar; but there are 28 peculiar genera, 6 belonging to the Scincidæ, 1 to the Acontiadæ, 5 to the Geckotidæ, and 16 to the Agamidæ. Many lizards being sand and desert-haunters, it is not surprising that a number of forms are common to the borderlands of the Oriental and Ethiopian regions; yet the Sepidæ, so abundant in all Africa, do not range to the peninsula of India; and the equally Ethiopian Zonuridæ have only one Oriental species, found, not in the peninsula but in the Khasya Hills. The Acontiadæ alone offer some analogy to the distribution of the Lemurs, being found in Africa, Madagascar, Ceylon, and the Moluccas.
The Australian region has 11 families, 3 of which arepeculiar; and it has about 40 peculiar genera in ten families, about half of these genera belonging to the Scincidæ. Only 3 families of almost universal distribution are common to the Australian and Neotropical regions, with one species of the American Iguanidæ in the Fiji Islands, so that, as far as this order is concerned, these two regions have little resemblance.
The Neotropical region has 15 families, 6 of which are peculiar to it, and it possesses more than 50 peculiar genera. These are distributed among 12 families, but more than half belong to the Iguanidæ, and half the remainder to the Teidæ,—the two families especially characteristic of the Neotropical region. All the Nearctic families which are not of almost universal distribution are peculiarly Neotropical, showing that the Lacertilia of the former region have probably been derived almost exclusively from the latter.
On the whole the distribution of the Lacertilia shows a remarkable amount of specialization in each of the great tropical regions, whence we may infer that Southern Asia, Tropical Africa, Australia, and South America, each obtained their original stock of this order at very remote periods, and that there has since been little intercommunication between them. The peculiar affinities indicated by such cases as the Lepidosternidæ, found only in the tropics of Africa and South America, andTachydromusin Eastern Asia and West Africa, may be the results either of once widely distributed families surviving only in isolated localities where the conditions are favourable,—or of some partial and temporary geographical connection, allowing of a limited degree of intermixture of faunas. The former appears to be the more probable and generally efficient cause, but the latter may have operated in exceptional cases.
Fossil Lacertilia.
These date back to the Triassic period, and they are found in most succeeding formations, but it is not till the Tertiary period that forms allied to existing genera occur. These are at present too rare and too ill-defined to throw much light on the geographical distribution of the order.
Order III.—RHYNCOCEPHALINA.
Family53.—RHYNCOCEPHALIDÆ. (1 Genus, 1 Species.)
The singular and isolated genusHatteria—the "Tuatara" or fringed lizard—which alone constitutes this family, has peculiarities of structure which separate it from both lizards and crocodiles, and mark it out as an ancestral type, as distinct from other living reptiles as the Marsupials are from other Mammalia. It is confined to New Zealand, and is chiefly found on small islands near the north-east coast, being very rare, if not extinct, on the main land. A fossil reptile namedHyperodapedon, of Triassic age, has been found in Scotland and India, and is supposed by Professor Huxley to be more nearly allied toHatteriathan to any other living animal.
Order IV.—CROCODILIA.
Family54.—GAVIALIDÆ. (2 Genera, 3 Species.)
The Gavials are long-snouted Crocodiles with large front teeth, and canines fitting in notches of the upper jaw. They consist of two genera,Gavialis(1 sp.), inhabiting the Ganges;Tomistoma(2 sp.), found in the rivers of Borneo and North Australia.
Family55.—CROCODILIDÆ. (1 Genus, 12 Species.)
The true Crocodiles, which have the canines in notches, and the large front teeth in pits in the upper jaw, are widely distributed over the tropical regions of the globe, inhabiting all the rivers of Africa, the shores and estuaries of India, Siam, and eastward to North Australia. Other forms inhabit Cuba, Yucatan, and Guatemala, to Ecuador and the Orinooko. Four species are Asiatic, one exclusively Australian, three African, and four American. These have been placed in distinct groups, but Dr. Günther considers them all to form one genus,Crocodilus.
Family56.—ALLIGATORIDÆ. (1 Genus, 10 Species.)
The Alligators, which are distinguished by having both the large front teeth and the canines fitting into pits of the upper jaw, are confined to the Neotropical, and the southern part of the Nearctic regions, from the lower Mississippi and Texas through all Tropical America, but they appear to be absent from the Antilles. They are all placed by Dr. Günther in the single genus,Alligator.
General Remarks on the Distribution of Crocodilia.
These animals, being few in number and wholly confined to the tropical and sub-tropical regions, are of comparativelylittle interest as regards geographical distribution. America possesses both Crocodiles and Alligators; India, Crocodiles and Gavials; while Africa has Crocodiles only. Both Crocodiles and Gavials are found in the northern part of the Australian region, so that neither of the three families are restricted to a single region.
Fossil Crocodilia.
The existing families of the order date back to the Eocene period in Europe, and the Cretaceous in North America. In the south of England, Alligators, Gavials and Crocodiles, all occur in Eocene beds, indicating that the present distribution of these families is the result of partial extinction, and a gradual restriction of their range—a most instructive fact, suggesting the true explanation of a large number of cases of discontinuous distribution which are sometimes held to prove the former union of lands now divided by the deepest oceans. In more ancient formations, a number of Crocodilian remains have been discovered which cannot be classed in any existing families, and which, therefore, throw no light on the existing distribution of the group.
Order V.—CHELONIA.
Family57.—TESTUDINIDÆ. (14 Genera, 126 Species.)
The Testudinidæ, including the land and many fresh-water tortoises, are very widely distributed over the Old and New worlds, but are entirely absent from Australia. They are especially abundant in the Nearctic region, as far north as Canada and British Columbia, and almost equally so in theNeotropical and Oriental regions; in the Ethiopian there is a considerable diminution in the number of species, and in the Palæarctic they are still less numerous, being confined to the warmer parts of it, except one species which extends as far north as Hungary and Prussia. The genera are:—
Testudo(25 sp.), most abundant in the Ethiopian region, but also extending over the Oriental region, into South Europe, and the Eastern States of North America;Emys(64 sp.), abundant in North America and over the whole Oriental region, less so in the Neotropical and the Palæarctic regions;Cinosternon(13 sp.), United States and California, and Tropical America;Aromochelys(4 sp.), confined to the Eastern States of North America;Staurotypus(2 sp.), Guatemala and Mexico;Chelydra(1 sp.), Canada to Louisiana;Claudius(1 sp.), Mexico;Dermatemys(3 sp.), South America, Guatemala, and Yucatan;Terrapene(4 sp.), Maine to Mexico, Sumatra to New Guinea, Shanghae and Formosa—a doubtfully natural group;Cinyxis(3 sp.),Pyxis(1 sp.),Chersina(4 sp.), are all Ethiopian;Dumerilia(1 sp.), is from Madagascar only.
Family58.—CHELYDIDÆ. (10 Genera, 44 Species.)
The Chelydidæ, or fresh-water tortoises with imperfectly retractile heads, have a remarkable distribution in the three great southern continents of Africa, Australia, and South America; the largest number of species being found in the latter country. The genera are:—
Peltocephalus(1 sp.),Podocnemis(6 sp.),Hydromedusa(4 sp.),Chelys(1 sp.), andPlatemys(16 sp.), inhabiting South America from the Orinooko to the La Plata, the latter genus occurring also in Australia and New Guinea;Chelodina(5 sp.),Chelemys(1 sp.), andElseya(2 sp.) from Australia; whileSternotheres(6 sp.), andPelomedusa(3 sp.), inhabit Tropical and South Africa and Madagascar.
Family59.—TRIONYCHIDÆ. (3 Genera, 25 Species.)
The distribution of the Trionychidæ, or Soft Tortoises, is very different from that of the Chelydidæ, yet is equally interesting. They abound most in the Oriental region, extending beyond it to Northern China and Japan. In the Nearctic region they are only found in the Eastern States, corresponding curiously to the distribution of plants, in which the affinity of Japan to the Eastern States is greater than to California. The Trionychidæ are also found over the Ethiopian region, but not in Madagascar.
The genera are,—Trionyx(17 sp.), which extends over the whole area of the family as above indicated;Cycloderma(5 sp.), peculiar to Africa;Emyda(3 sp.), the peninsula of India, Ceylon, and Africa.
Family60.—CHELONIIDÆ. (2 Genera, 5 Species.)
General Distribution.—All the warm and tropical Seas.
The Marine Turtles are almost universally distributed.Dermatochelys(1 sp.), is found in the temperate seas of both the Northern and Southern Hemispheres;Chelone(4 sp.), ranges over all the tropical seas—C. viridis, the epicureans' species, inhabiting the Atlantic, whileC. imbricatawhich produces the "tortoiseshell" of commerce is found in the Indian and Pacific oceans.
Remarks on the Distribution of the Chelonia.
The four families into which the Chelonia are classed have all of them a wide distribution, though none are universal. The Ethiopian region seems to be the richest, as it possesses 3 of the four families, while no other region has more than 2; and it also possesses 7 peculiar genera. Next comes the Neotropical region with 2 families and 6 peculiar genera; the Australian with 3, and the Nearctic with 2 peculiar genera; while the Oriental and Palæarctic regions possess none that are peculiar. There are about 30 genera and 200 species in the whole order.
Fossil Chelonia.—The earliest undoubted remains of this order occur in the Upper Oolite. These belong to the Cheloniidæ and Emydidæ, which are also found in the Chalk. In the Tertiary beds Chelonia are more abundant, and the Trionychidæ now appear. The Testudinidæ are first met with in the Miocene formation of Europe and the Eocene of North America, the most remarkable being the giganticColossochelys Atlasof the Siwalik Hills. It appears, therefore, that the families of the order Chelonia were already specialised in the Secondary period, a fact which, together with their more or less aquatic habits, sufficiently accounts for their generally wide distribution. Species ofTestudo,Emys, andTrionyx, are found in the Upper Miocene of the south of France.
AMPHIBIA.
Order I.—PSEUDOPHIDIA.
Family1.—CÆCILIADÆ. (4 Genera, 10 Species.)
The Cæciliadæ are a curious group of worm-like Amphibia sparingly scattered over the three great tropical regions. The genera are,—Cæcilia, which inhabits West Africa, Malabar and South America;Siphonopsis, peculiar to Brazil and Mexico;Ichthyopsis, from Ceylon and the Khasya Mountains; andRhinatremafrom Cayenne.
Order II.—URODELA.
Family2.—SIRENIDÆ. (1 Genus, 3 Species.)
The genusSiren, consisting of eel-like Batrachians with two anterior feet and permanent branchiæ, inhabits the South-Eastern States of North America from Texas to Carolina.
Family3.—PROTEIDÆ. (2 Genera, 4 Species.)
The Proteidæ have four feet and persistent external branchiæ. The two genera are,—Proteus(1 sp.), found only in caverns of Central Europe; andMenobranchus, which are like newts in form, and inhabit the Eastern States of North America.
Family4.—AMPHIUMIDÆ. (1 Genus, 2 Species.)
The genusAmphiuma, orMurænopsis, consists of slender eel-like creatures with four rudimentary feet, and no external branchiæ. The species inhabit the Southern United States from New Orleans to Carolina.
Family5.—MENOPOMIDÆ. (2 Genera, 4 Species.)
There are large Salamanders of repulsive appearance, found only in Eastern Asia and the Eastern United States. The genera are,—Sieboldia(2 sp.), Japan and north-west China;Menopoma=Protonopsis(2 sp.), Ohio and Alleghany rivers.
Family6.—SALAMANDRIDÆ. (20 Genera, 85 Species.)
The Salamandridæ, of which our common Newts are characteristic examples, form an extensive family highly characteristic of the North Temperate regions, a few species only extending into the Neotropical region along the Andes to near Bogota, and one into the Oriental region in Western China. The genera, as arranged by Dr. Strauch, are as follows:—
Salamandra(2 sp.), Central and South Europe and North Africa;Pleurodeles(1 sp.), Spain, Portugal, and Morocco;Bradybates(1 sp.), Spain;Triton(16 sp.), all Europe except the extreme north, Algeria, North China and Japan, Eastern States of North America, California and Oregon;Chioglossa(2 sp.), Portugal and South Europe;Salamandrina(1 sp.), Italy to Dalmatia;Ellipsoglossa(2 sp.), Japan;Isodactylium(2 sp.), East Siberia;Onychodactylus(1 sp.), Japan;Amblystoma(21 sp.), Nearctic region from Canada and Oregon to Mexico, most abundant in Eastern States;Ranodon(1 sp.), Tartary and North-east China;Dicamptodon(1 sp.), California;Plethodon(5 sp.), Massachusetts to Louisiana, and Vancouver's Island to California;Desmognathus(4 sp.), Eastern United States south of latitude 43°;Anaides(1 sp.), Oregon and Northern California;Hemidactylium(2 sp.), South-eastern United States and Southern California;Heredia(1 sp.), Oregon and California;Spelerpes(18 sp.), Eastern United States from Massachusetts to Mexico, Guatemala, Costa Rica and Andes of Bogota, with a species in South Europe;Batrachoseps(2 sp.), South-eastern United States and California;Tylotriton(1 sp.), Yunan in West China.
Order III.—ANURA.
Family7.—RHINOPHRYNIDÆ. (1 Genus, 1 Species.)
The Rhinophrynidæ are Toads with imperfect ears and a tongue which is free in front. The single species ofRhinophrynus, is a native of Mexico.
Family8.—PHRYNISCIDÆ. (5 Genera, 13 Species.)
The Phryniscidæ, or Toads with imperfect ears and tongue fixed in front, are widely distributed over the warmer regions of the earth, but are most abundant in the Neotropical region and Australia, while only single species occur in the Old World. The genera are:—
Phryniscus(7 sp.), from Costa Rica to Chili and Monte Video;Brachycephalus(1 sp.), Brazil;Pseudophryne(3 sp.), Australia and Tasmania;Hemisus(1 sp.), Tropical Africa;Micrhyla(1 sp.), Java.
Family9.—HYLAPLESIDÆ. (1 Genus, 5 Species.)
The Hylaplesidæ are Toads with perfect ears, and they seem to be confined to the Neotropical region. The only genus,Hylaplesia(5 sp.), inhabits Brazil, Chili, and the Island of Hayti.
Family10.—BUFONIDÆ. (6 Genera, 64 Species.)
The rather extensive family of the Bufonidæ, which includes our common Toad, and is characterised by prominent neck glands and tongue fixed in front, is almost universally distributed, but is very rare in the Australian region; one species being found in Celebes and one in Australia. The genera are:—
Kalophrynus(2 sp.), Borneo;Bufo(58 sp.), has the range of the entire family, except Australia;Otilophus(1 sp.), South America;Peltaphryne(1 sp.), Porto Rico;Pseudobufo(1 sp.), Malay Peninsula;Schismaderma(1 sp.), Natal;Notaden(1 sp.), East Central Australia.
Family11.—XENORHINIDÆ. (1 Genus, 1 Species.)
The Xenorhinidæ may be characterised as Toads with perfect ears and tongue free in front. The only species ofXenorhinais a native of New Guinea.
Family12.—ENGYSTOMIDÆ. (15 Genera, 31 Species.)
The Engystomidæ are Toads without neck-glands and with the tongue tied in front. They are most abundant in the Oriental and Neotropical regions, especially in the latter, which contains about half the known species, with isolated species in Australia, Africa, and the Southern States of North America. They appear to be the remnant of a once extensive and universally distributed group, which has maintained itself in two remote regions, but is dying out everywhere else. The genera are:—
Engystoma(9 sp.), Carolina to La Plata, with one species in South China;Diplopelma(3 sp.), South India to China and Java;Cacopus(2 sp.), Central India;Glyphoglossus(1 sp.), Pegu;Callula(4 sp.), Sikhim, Ceylon, China, and Borneo;Brachymerus(1 sp.), South Africa;Adenomera(1 sp.), Brazil;Pachybatrachus(1 sp.), Australia;Breviceps(2 sp.), South and West Africa;Chelydobatrachus(1 sp.), West Australia;Hypopachus(1 sp.), Costa Rica;Rhinoderma(1 sp.), Chili;Atelopus(1 sp.), Cayenne and Peru;Copea(1 sp.), South America;Paludicola(1 sp.), New Granada.
Family13.—BOMBINATORIDÆ. (8 Genera, 9 Species.)
The Bombinatoridæ are a family of Frogs which have imperfect ears and no neck-glands, and they have a very peculiar andinteresting distribution, being confined to Central and South Europe, the southern part of South America, and New Zealand. They consist of many isolated groups forming five separate sub-families. The genera are:—
Bombinator, Central Europe and Italy;PelobatesandDidocus, Central Europe and Spain;Telmatobius(2 sp.), Peru and Brazil;Alsodes, Chonos Archipelago;Cacotus, Chili;Liopelma, New Zealand;Nannophryne, Straits of Magellan.
Family14.—PLECTROMANTIDÆ. (1 Genus, 1 Species.)
The Plectromantidæ, which are Frogs with neck-glands, and the toes but not the fingers dilated, consists of a single species of the genusPlectromantis. It inhabits the region west of the Andes, and south of the Equator.
Family15.—ALYTIDÆ. (5 Genera, 37 Species.)
The Alytidæ are Frogs with neck-glands and undilated toes. They are most abundant in the Ethiopian region, with a few species in the Nearctic and Australian regions, and one in Europe and Brazil respectively. The genera are:—
Alytes(1 sp.), Central Europe;Scaphiopus(5 sp.), California to Mexico and the Eastern States;Hyperolius(29 sp.), all Africa, and two in New Guinea and North Australia;Helioporus(1 sp.), in Australia;Nattereria(1 sp.), Brazil.