410 PALEONTOLOGY OF NEW-YORK. 



Genus VixutixA (Hall). 



ViTcuiTA : Hall, Thirteenth Report on the State Cabinet, p. 72. 1860. 



Shell plano-convex : hinge-line extended : valves articulating by teeth 



and sockets. 

 Ventral valve gibbous, with a high area, and large triangular fissure. A 



callosity or false area in the bottom of the fissure. Dental lamelljB 



thick and strong. 

 Dorsal valve depressed-convex, with a scarcely perceptible area; a 



strong cardinal process, which is conspicuous at the base of the fissure 



in the closed valves. 

 Surface plicated, papillose : shell-structure punctate. 



Titalina pnstnlosa. 



PLATE LXIL 



Vitulina pustuloia : Hali, in Thirteenth Report on the State Cabinet, p. 82. 1800. 



Shell subplano-convex, semielliptical : hinge-line equalling or a little 

 less than the width of the shell : surface marked by a few strong pli- 

 cations, and covered by minute papillie, which appear like the bases 

 of setae. Substance of the shell finely punctate. 



Ventral valve very convex ; the apex a little arcuate, subangular in the 

 middle above, and the elevation continued in a broad fold which is at 

 first flattened and then becomes grooved or duplicate below, with four 

 or five rounded or subangular plications on each side ; the area much 

 elevated, and the margin sloping rapidly from the apex to the cardinal 

 extremities : foramen large and wide, being half the length of the 

 area, and reaching to the apex ; deltidial pieces or pseudo-deltidium 

 unknown. 



Dorsal valve flat or slightly convex, with a wide mesial depression 

 which is nearly flat in the bottom, and in larger specimens has a shal- 

 low groove in the middle towards the front. The plications on the 

 sides correspond with those of the ventral valve. There is a narrow 

 scarcely perceptible area. 



