188 



CYPRINIDiE. 



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 a sharp ridge. The form of the shell strongly recalls 

 Heniicardium. Gyh. 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 eMiptica, 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. (cxv, 35). In this group also, the 

 distinction from typical Cyprina appears to be unimportant. 



GrONiosoMA, Conrad, 1869. 



Distr. — G. injiata^ 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, 



Yeniella, Stoliczka, 1870. 



/S?/w.— Yenilia, Morton, 1834, not Duponchel, 1829, nor Alder 

 and Hancock. 



Distr. — Jurassic — Tertiary; U. S., Europe. F. tumida, Nyst. 

 (cxv, 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 A^alve 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 



