188 CYPRINIDA. 
plain ; siphonal orifices close together, fringed, slightly projecting ; 
outer gills semilunar, inner truncated in front. 
The principal hinge-tooth in the right valve of Cyprina repre- 
sents the second and third in Venus and Cytherea; the second 
tooth of the left valve is consequently obsolete. 
CICATREA, Stoliczka, 1870. Shell with a sharp, high ridge; 
beaks distant and strongly incurved, with a short deeply bifurcate 
groove running posteriorly from each, in which is lodged the 
ligament ; posterior cardinal teeth rather narrow in both valves 
(while in Cyprina proper the one in the right valve is very thick 
and bifurcate); the two anterior cardinals in the left valve are 
very large, the same superimposed teeth in the right valve, how- 
ever, very small; the anterior muscular impression is anteriorly 
margined by asharpridge. The form of the shell strongly recalls 
Hemicardium. Cyz. cordialis, Stol. Cretaceous; India. 
CYPRINOPSIS, Conrad, 1869, is characterized as equivalve, two 
anterior cardinal teeth and one very oblique tooth in the right 
valve, pallial line entire. Artemis ellipltica, Smith. Does not 
appear to differ much from a typical Cyprina. 
VELEDA, Conrad, 1870. Ovately elongated, tumid, posteriorly 
ridged from the umbo, concentrically striated on the surface, 
equivalved ; left valve with a A—shaped cardinal tooth under the 
apex and three compressed teeth, posterior one elongated and 
parallel with the dorsal margin, cardinal plate channeled, deeply 
so anteriorly. V. lintea, Con. (exv, 35). In this group also, the 
distinction from typical Cyprina appears to be unimportant. 
Gonrosoma, Conrad, 1869. 
Distr.—G. inflata, Conr. Cret.; New Jersey. 
Shell subquadrangular, moderately tumid, angular along the 
region from the beak to the infero-posterior end; muscular 
impressions marginal, pallial line—? hinge in the right valve 
with two prominent cardinal teeth and a long anterior lateral, 
parallel with the hinge-margin. 
VENIELLA, Stoliczka, 1870. 
Syn.—Venilia, Morton, 1834, not Duponchel, 1829, nor Alder 
and Hancock. . 
Distr.—Jurassic—Tertiary ; U. 8., Europe. V. tumida, Nyst. 
(exv, 53). 
Shell ventricose, inflated, umbonal slope posteriorly angulate, 
with the beaks outwardly incurved, more or less distant, a long 
narrow ligamental furrow running from them posteriorly, hinge 
with three cardinal and one posterior lateral tooth in each valve; 
right valve with the supra-posterior cardinal tooth, generally 
bifid anteriorly with a hook-like downward bent prolongation, 
infero-anterior cardinal smaller, lamelliform, or more or less 
tubercular, separated from the other tooth by a more or less 
