FOOTNOTES:[126]Three very interesting bivalve shells, distinct, it appears, from the other species of the genera to which they respectively belong, have been discovered in the above-mentioned river by Major Denham. The first, a species ofÆtheria, I distinguish asÆtheriaDenhami: testa irregulariter rotundato-oblonga, ad cardinem gibbosa, utriusque valvæ callo cardinali basim versus oblique truncato.Hab. in Africæ interioris fluvio Gammaroo.The form of the cardinal callosity to which the semi-internal ligament is attached affords a distinction sufficiently characteristic of the species: its oblique truncating plane, which extends towards the rather indistinct umbo, is, in the closed state of the shell, in partial contact with that of the corresponding and similarly formed callus of the other valve. The general form of the shell is oblong or rounded, but appears to be subject to considerable variation: one of the specimens before me exhibits the exterior of Lamarck’s A.transversa, which latter is no doubt a casual variety only of the other species described and figured by that naturalist.These shells are externally furnished with a blackish-brown epidermis; beneath this a white film is deposited, on the removal of which a beautiful pearly naker appears, similar to that of the internal surface of the valves. The blistered appearance of the interior of both the valves is constant in all specimens, and may, as intimately connected with the structure of the shell, be considered of sufficient importance to be admitted into the distinctive character of the genus.Lamarck, imagining that these shells live at the bottom of the sea, named the genus, as he says, after one of the daughters of Oceanus. Though the Ætheriæ are now well known to be fluviatile shells, the emendators of zoological nomenclature may still be exonerated from framing a new name for this genus, since the old one is derivable from the original locality of its species; a part of central Africa having, according to Pliny, been anciently known by the appellation ofÆtheria.The second shell, a new species ofIridina, may be thus characterized:IridinaOudnæi: testa transversa ovato-lanceolata tumidiuscula, cardine stricto sub-edentulo, basis margine sinuato.Hab. cum priore.This species is very distinct from E.elongatain form and in the hinge line being without crenulation; and from E.nilotica, which it resembles in the latter of those characters, it differs by its form, inferior thickness, and iridescence. The length of the specimen before me is 4⅔, its greatest breadth at the umbo nearly two inches. Placed on the basal edge, which is concave, the anterior side presents a considerable slope from the umbo to the exterior margin, which gives the valves a tapering or ovate-lanceolate form. The external epidermis, of a greenish-brown colour, exhibits slightly undulating striæ of growth. The interior surface is slightly uneven-undulated, white, with delicate opalescent colours, green and faint pink; the former chiefly disposed in spots. The muscular impressions are more slightly marked than in the other species.For the third shell, which I considered as a new species ofAnodon, I propose the name ofAnodonClappertoni: testa transversim oblonga, antice in extremo cardine acute excisa.Hab. cum antecedentibus.The notch at the anterior extremity of the hinge being always acute, never obtusangular or rounded, I have confined myself to it in the distinctive character of this species, which differs in several other respects fromAnodonpurpureusandrugosusof Swainson, to both of which it is, however, nearly related. The size of the shell, in the several specimens before me, varies from 1½ by ¾ of an inch to 3 inches by nearly 1½. Its form is transverse-oval, with a slight slope at the anterior end. The hinge margin is straight. Epidermis olive-green, appearing of a reddish-brown colour, owing to the pink colour of the surface underneath, which latter in one specimen passes into bluish-green at the umbones. Muscular impressions three; one of them, at the anterior end, oval, and continued in a faint tapering form towards the hollow of the umbo; of the two other impressions, which are both stronger marked, the one nearest to the edge of the valve is oval, with a small rounded sinus at the inner border, and close to it a smaller irregularly oval mark with notched margin: the two principal marks are connected by the edge of the impression of the mantle, the smaller mark being placed within the line. The tinge of the internal surface is pink, imperfectly painted over as it were with white. The several specimens, in different stages of growth, exhibit all these characters; there is, however, among them a single valve of rather larger dimensions and more rounded than the rest, with a fine bronze-coloured internal surface like that ofIridinanilotica. Whether this is to be considered as a distinct species, or only as a variety indicative of the full grown state of the shell, I must leave to the decision of conchologists more experienced in discriminating the ambiguous species of this genus.
FOOTNOTES:
[126]Three very interesting bivalve shells, distinct, it appears, from the other species of the genera to which they respectively belong, have been discovered in the above-mentioned river by Major Denham. The first, a species ofÆtheria, I distinguish asÆtheriaDenhami: testa irregulariter rotundato-oblonga, ad cardinem gibbosa, utriusque valvæ callo cardinali basim versus oblique truncato.Hab. in Africæ interioris fluvio Gammaroo.The form of the cardinal callosity to which the semi-internal ligament is attached affords a distinction sufficiently characteristic of the species: its oblique truncating plane, which extends towards the rather indistinct umbo, is, in the closed state of the shell, in partial contact with that of the corresponding and similarly formed callus of the other valve. The general form of the shell is oblong or rounded, but appears to be subject to considerable variation: one of the specimens before me exhibits the exterior of Lamarck’s A.transversa, which latter is no doubt a casual variety only of the other species described and figured by that naturalist.These shells are externally furnished with a blackish-brown epidermis; beneath this a white film is deposited, on the removal of which a beautiful pearly naker appears, similar to that of the internal surface of the valves. The blistered appearance of the interior of both the valves is constant in all specimens, and may, as intimately connected with the structure of the shell, be considered of sufficient importance to be admitted into the distinctive character of the genus.Lamarck, imagining that these shells live at the bottom of the sea, named the genus, as he says, after one of the daughters of Oceanus. Though the Ætheriæ are now well known to be fluviatile shells, the emendators of zoological nomenclature may still be exonerated from framing a new name for this genus, since the old one is derivable from the original locality of its species; a part of central Africa having, according to Pliny, been anciently known by the appellation ofÆtheria.The second shell, a new species ofIridina, may be thus characterized:IridinaOudnæi: testa transversa ovato-lanceolata tumidiuscula, cardine stricto sub-edentulo, basis margine sinuato.Hab. cum priore.This species is very distinct from E.elongatain form and in the hinge line being without crenulation; and from E.nilotica, which it resembles in the latter of those characters, it differs by its form, inferior thickness, and iridescence. The length of the specimen before me is 4⅔, its greatest breadth at the umbo nearly two inches. Placed on the basal edge, which is concave, the anterior side presents a considerable slope from the umbo to the exterior margin, which gives the valves a tapering or ovate-lanceolate form. The external epidermis, of a greenish-brown colour, exhibits slightly undulating striæ of growth. The interior surface is slightly uneven-undulated, white, with delicate opalescent colours, green and faint pink; the former chiefly disposed in spots. The muscular impressions are more slightly marked than in the other species.For the third shell, which I considered as a new species ofAnodon, I propose the name ofAnodonClappertoni: testa transversim oblonga, antice in extremo cardine acute excisa.Hab. cum antecedentibus.The notch at the anterior extremity of the hinge being always acute, never obtusangular or rounded, I have confined myself to it in the distinctive character of this species, which differs in several other respects fromAnodonpurpureusandrugosusof Swainson, to both of which it is, however, nearly related. The size of the shell, in the several specimens before me, varies from 1½ by ¾ of an inch to 3 inches by nearly 1½. Its form is transverse-oval, with a slight slope at the anterior end. The hinge margin is straight. Epidermis olive-green, appearing of a reddish-brown colour, owing to the pink colour of the surface underneath, which latter in one specimen passes into bluish-green at the umbones. Muscular impressions three; one of them, at the anterior end, oval, and continued in a faint tapering form towards the hollow of the umbo; of the two other impressions, which are both stronger marked, the one nearest to the edge of the valve is oval, with a small rounded sinus at the inner border, and close to it a smaller irregularly oval mark with notched margin: the two principal marks are connected by the edge of the impression of the mantle, the smaller mark being placed within the line. The tinge of the internal surface is pink, imperfectly painted over as it were with white. The several specimens, in different stages of growth, exhibit all these characters; there is, however, among them a single valve of rather larger dimensions and more rounded than the rest, with a fine bronze-coloured internal surface like that ofIridinanilotica. Whether this is to be considered as a distinct species, or only as a variety indicative of the full grown state of the shell, I must leave to the decision of conchologists more experienced in discriminating the ambiguous species of this genus.
[126]Three very interesting bivalve shells, distinct, it appears, from the other species of the genera to which they respectively belong, have been discovered in the above-mentioned river by Major Denham. The first, a species ofÆtheria, I distinguish as
ÆtheriaDenhami: testa irregulariter rotundato-oblonga, ad cardinem gibbosa, utriusque valvæ callo cardinali basim versus oblique truncato.
Hab. in Africæ interioris fluvio Gammaroo.
The form of the cardinal callosity to which the semi-internal ligament is attached affords a distinction sufficiently characteristic of the species: its oblique truncating plane, which extends towards the rather indistinct umbo, is, in the closed state of the shell, in partial contact with that of the corresponding and similarly formed callus of the other valve. The general form of the shell is oblong or rounded, but appears to be subject to considerable variation: one of the specimens before me exhibits the exterior of Lamarck’s A.transversa, which latter is no doubt a casual variety only of the other species described and figured by that naturalist.
These shells are externally furnished with a blackish-brown epidermis; beneath this a white film is deposited, on the removal of which a beautiful pearly naker appears, similar to that of the internal surface of the valves. The blistered appearance of the interior of both the valves is constant in all specimens, and may, as intimately connected with the structure of the shell, be considered of sufficient importance to be admitted into the distinctive character of the genus.
Lamarck, imagining that these shells live at the bottom of the sea, named the genus, as he says, after one of the daughters of Oceanus. Though the Ætheriæ are now well known to be fluviatile shells, the emendators of zoological nomenclature may still be exonerated from framing a new name for this genus, since the old one is derivable from the original locality of its species; a part of central Africa having, according to Pliny, been anciently known by the appellation ofÆtheria.
The second shell, a new species ofIridina, may be thus characterized:
IridinaOudnæi: testa transversa ovato-lanceolata tumidiuscula, cardine stricto sub-edentulo, basis margine sinuato.
Hab. cum priore.
This species is very distinct from E.elongatain form and in the hinge line being without crenulation; and from E.nilotica, which it resembles in the latter of those characters, it differs by its form, inferior thickness, and iridescence. The length of the specimen before me is 4⅔, its greatest breadth at the umbo nearly two inches. Placed on the basal edge, which is concave, the anterior side presents a considerable slope from the umbo to the exterior margin, which gives the valves a tapering or ovate-lanceolate form. The external epidermis, of a greenish-brown colour, exhibits slightly undulating striæ of growth. The interior surface is slightly uneven-undulated, white, with delicate opalescent colours, green and faint pink; the former chiefly disposed in spots. The muscular impressions are more slightly marked than in the other species.
For the third shell, which I considered as a new species ofAnodon, I propose the name of
AnodonClappertoni: testa transversim oblonga, antice in extremo cardine acute excisa.
Hab. cum antecedentibus.
The notch at the anterior extremity of the hinge being always acute, never obtusangular or rounded, I have confined myself to it in the distinctive character of this species, which differs in several other respects fromAnodonpurpureusandrugosusof Swainson, to both of which it is, however, nearly related. The size of the shell, in the several specimens before me, varies from 1½ by ¾ of an inch to 3 inches by nearly 1½. Its form is transverse-oval, with a slight slope at the anterior end. The hinge margin is straight. Epidermis olive-green, appearing of a reddish-brown colour, owing to the pink colour of the surface underneath, which latter in one specimen passes into bluish-green at the umbones. Muscular impressions three; one of them, at the anterior end, oval, and continued in a faint tapering form towards the hollow of the umbo; of the two other impressions, which are both stronger marked, the one nearest to the edge of the valve is oval, with a small rounded sinus at the inner border, and close to it a smaller irregularly oval mark with notched margin: the two principal marks are connected by the edge of the impression of the mantle, the smaller mark being placed within the line. The tinge of the internal surface is pink, imperfectly painted over as it were with white. The several specimens, in different stages of growth, exhibit all these characters; there is, however, among them a single valve of rather larger dimensions and more rounded than the rest, with a fine bronze-coloured internal surface like that ofIridinanilotica. Whether this is to be considered as a distinct species, or only as a variety indicative of the full grown state of the shell, I must leave to the decision of conchologists more experienced in discriminating the ambiguous species of this genus.
Thermometrical Journal kept at Kouka in Bornou.