VENERIDZ. 117 
MARCIA, H, and A. Adams, 1854. Surface of the valves smooth. 
V. undulosa, Lam. (exiii, 18). 
KATELYSIA, Rémer, 1857.  V. scalarina, Lam. 
ANAITIS, Rémer, 1857. (Clausina, Brown.) Includes the 
moderately tumid cordate forms with strong concentric lamelle. 
V. plicata, Gmel. 
GOMPHINA, Morch, 1385p. Shell ovate, cordate, moderately 
inflated, smooth; hinge-teeth the same as in typical Chione. 
Romer describes four species, and considers V. undulosa, Lam., 
as the type, while H. and A. Adams quote V. donacina, Chemn. 
(exiii, 19}, as the only species, and place it as a subgenus of 
Cytherea (= Meretrix). 
votupPrA, Defrance, 1829. Shell minute, Isocardia-shaped 
concentrically ribbed, with a large lunule. V. rugosa, Defy. 
Eocene ; Hauteville. 
Psepuis, Carpenter, 1865. 
Distr.—3 sp. California. P. Lordi, Carp. 
Shell thin, rounded or quadrangular, somewhat inflated ; 
pallial sinus small; three elongated thin cardinal teeth in each 
valve. Oviparous, like Spherium. 
CytTHEerEA, Lam., 1805. 
Etym.— Cytherea, from Cythera, an Adgean island. 
Syn.—Meretrix, Lam., 1799.. Callistoderma, Poli, 1791. Cor- 
bicula, Benson. 
Distr.—Same as Venus. Recent 150 sp. Fossil, 80sp. Cre- 
taceous—. C. petechialis, Lam. (exiii, 20). 
Shell like Venus, oval-triangular, smooth ; margins simple ; 
hinge with three cardinal teeth and an anterior tooth beneath 
the lunule; pallial sinus moderate, angular. 
Animal with plain mantle-margins ; siphons united half-way. 
CALLISTA, Poli, 1791. Shell oval, transverse, inequilateral ; 
pallial sinus suboval, profound. Mantle-margins folded and 
cirrous above the siphons; siphons united, cirrated at their 
extremities. (C. erycina, Linn. (exiii, 21). 
TIVELA, Link, 1807. (Trigona, Muhlf.,1811.) Shell triangular, 
subequilateral, cuneiform; three to five cardinal teeth in one 
valve, four to six in the other; anterior lateral tooth narrow, 
elongated, compressed ; pallial impression with a short oblique 
or sometimes horizontal sinus. 28 sp. W. Indies, Mediterra- 
nean, Senegal, Cape, India, West America. Fossil. Miocene ; 
Bordeaux. C. radiata, Sowb. (exiii, 22). 
PACHYDESMA, Conr. (Trigonella, Conr., 1837.) C. crassatel- 
loides, Conr., attains a diameter of five inches, and is very 
ponderous. 
APHRODINA, Conrad, 1868. Shell rounded or suboval, striated 
or suleated ; hinge in the left valve with three diverging cardinal 
