CORBULID. 141 
for the purpose of supporting the cartilage, which seems likely , 
has yet to be satisfactorily determined. 
SpHENTOpSIS, Sandberger, 1863. 
Distr.S. scalaris, Braun. Tertiary; Germany (cv, 1-3). 
Shell subtrigonal, compressed, equivalve, posteriorly rostrate 
and slightly gaping; hinge of right valve with an anterior car- 
dinal tooth, and a deep cartilage-pit behind it, a long laminar 
tooth runs along the areal margin; left valve edentulous, only 
provided with a cartilage-pit ; pallial sinus deep. 
Nr#ra, Gray, 1834. 
Etym.—Nexra, a Roman lady’s name. 
Syn.—Cuspidaria, Nardo, 1840. Sphena, d’Orb., 1846. 
Distr.—22 sp. Norway, Britain, Mediterranean, Canaries, 
Madeira, China, Moluccas, New Guinea, Chili; from 12-200 
fathoms. Fossil, 14 sp. Oolite—; Britain, Belgium, Italy. NV. 
ornatissima, Orb. (ev, 4, 5). 
Shell globular, attenuated, and gaping behind; right valve a 
little the smallest; umbones strengthened internally by a rib 
on the posterior side; cartilage-process spatulate, in each valve 
(furnished with a movable ossicle—Deshayes), with an obsolete 
tooth in front, and a posterior lateral tooth; pallial sinus very 
shallow. 
Animal with the mantle closed; fcot lanceolate; siphons 
short, united, branchial largest, anal with a membranous valve, 
both with a few long, lateral cirri. 
Placed by Messrs. Adams in the Anatinide, though judging 
from the form of the shell, being in many respects similar to 
that of Corbula, and also from the form of the small foot and the 
short siphons of the animal, there can be little doubt that Des- 
hayes’ classification near Sphzenia, Corbula, etc., is the more 
correct one. Almost the only character which some species of 
the genus have in common with the Anatinide is the presence of 
a small ossicle at the cartilage, but as all the Anatinide do not 
possess the same, its presence cannot be regarded as an exclu- 
sive character of that family. 
ruinoMyA, A. Ad., 1864. For those forms having the surface 
of the shells lamellar, like Nezera proper, but possessing a small 
triangular cartilage-pit, and two lateral teeth in the right valve. 
N. Philippinensis, Hinds. 
carpiomyA, A. Ad., 1864. Species with the surface radiately 
ribbed. N. Gouldiana, Hinds. 
CorsuLomyA, Nyst., 1846. 
Etym.—Corbula and Mya. 
Distr.—3 sp. Mediterranean. Fossil, 7 sp. Eocene; France, 
Belgium, England. C. antiqua, Desh. (evii, 38). 
