ACEPHALA. AL7 
stitits convextusculis) concentrice striata, epidermide fulvo induta ; 
apice mediano, acuto, obliquo ; cardo denie unico triangulart obliquo, 
instructus ; margine interno sulcato. 
Cardita procera, GouLp; Proceed. Boston Soc. Nat. Hist., ili. 276. 
July 1850. Expedition Shells, 83. 
SHELL small, elevated, height and breadth equal, equilateral, slightly 
convex, quadrant-shaped, with about fifteen radiating sulci, the inter- 
spaces forming rounded, slightly elevated ribs; concentrically striate, 
with occasionally a larger one indicating a stage of growth : apex acute, 
slightly curved, margin in front of it a little excurved; cavity of inte- 
rior small, margin crenulated, white: hinge with a single, triangular, 
oblique, strong tooth. 
Length three-fifths of an inch ; height three-fifths of an inch ; breadth 
one-fifth of an inch. 
Inhabits the mouth of Rio Negro, Patagonia. Couthouy. 
It has a more compressed and less oblique form than C. borealis, and 
fewer ribs. The right valve only was obtained. 
Figure 533, lateral view of the shell. 
CarDITA VENTRICOSA (Gould). 
Testa solida, ventricosa, ovato-trigona viz obliqua, radiatim ad viginte- 
costata, costis concentricée subnodosis, interstitiis angustis, epidermide 
fuliginoso, villoso induta ; apicibus submedianis, obtusis: intus alba ; 
margine profunde crenulato ; dente cardinali valvé dextre, elevato, 
crasso, triangulari. 
Cardita ventricosa, GouLp; Proceed. Boston Soc. Nat. Hist., i. 
276. July 1850. Expedition Shells, 83. 
Suet small, solid, very slightly oblique; beaks tumid, elevated, 
nearly central, slightly curved, eroded; valves tumid, with about 
eighteen or twenty rounded, well-defined, radiating ribs, which are 
105 
