TRANSACTIONS OF WAGNER 

 I ^20 



TERTIARY FAUNA OF FLORIDA 



and sharply circumscribed by an incised line ; there is no defined escutcheon ; 

 the ligament strong and elongated, fully exposed ; the pallial sinus is small, 

 pointed in front, horizontal, and free from the pallial line below ; the inner 

 valve margins are smooth in the type. The dental formula is ^°'°'°'°-. The 

 posterior right cardinal is slender but distinct ; the two in front of it and the 

 middle left cardinal are feebly bifid. The type recalls Mercenaria and some 

 species of the Callithaca group of Paphia. It is a native of the shores of South 

 America both on the Atlantic and Pacific. 



Subgenus Katelysia (Romer) Tr}-on. Type Venus scalarina Lamarck. 



Shell rounded trigonal, very inequilateral, subcompressed, sculptured with 

 concentric riblike ridges, sharper distally, polished, porcellanous, with an in- 

 conspicuous periostracum ; there is no radial sculpture ; coloration lively ; the 

 anterior end shorter ; lunule circumscribed and, with the undefined escutcheon, 

 smooth ; ligament short ; pallial sinus short, ascending, free below, blunt or 

 rounded in front ; teeth concentrated, the anterior right and posterior left car- 

 dinals slender, entire, the others grooved or bifid ; internal margins of the 

 valves smooth ; hinge-plate buttressed between the pedal scar and the scar of 

 the anterior adductor. 



The inequilateral ovate form of these shells is quite striking. The dental 

 formula is normal. Chameha Chenu, not Morch, is synonymous. 



Section Katelysia Romer {vide supra). 



Section Heinitapes Romer. Type Venus riinularis Lamarck. 



Shell subtrigonal, very tumid, otherwise essentially as in Katelysia, though 

 the aspect of the shells is very different on account of the difference in form. 



Section Venerella Cossmann. Type Venus hernwnvillensis Deshayes. 



Shells small, concentrically striate, ovate ; the lunule rather large, circum- 

 scribed ; the escutcheon not defined, internal margins entire ; the pallial sinus 

 small, ascending, free below, rounded in front : three teeth in each valve, the 

 edge of the hinge-plate excavated at the spaces between them ; the posterior 

 left cardinal long, bifid, the other teeth entire, the formula normal. 



These are distinguishable from the smaller species of Katelysia chiefly by 

 the form and disposition of the teeth. 



Section Mercimonia Dall, 1902. Type Venus Bernayi Cossmann, Cat. 

 Illustre, i., p. 95, pi. vi., figs. 11-13. 

 Shell small, ovate, concentrically striate, rather tumid ; hinge normal, the 



