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TERTIARY FAUNA OF FLORIDA 



33—35, 1848) ; = C. aliformis Conrad, Am. Journ. Conch., ii., p. 76, 1866 ; Shell 

 Bluff group, Vicksburg, Missis.sippi ; + C. (Tizd) aviara de Greg., Mon. 

 Ciaib., p. 234, pi. 37, figs. 12-14. 



Section Aitisofhyris Conrad. 

 Like Corbiila, but larger, with heavy, smooth shells, the beaks strongly 

 prosogyrate, thus twisting the plane of the ligament out of the vertical into 

 an oblique or nearly horizontal direction ; form very variable; inhabiting fresh 

 or brackish water. Type A. ohliqita Gabb. Fresh-water Tertiaries of the 

 Amazon. 



Section AnticOTbula Dall. 



Shell thin, the left valve larger, the hinge reversed; the ligament exter- 

 nal; resilium as in Anisothyris. Type A. [Hiniclla) flmnatilis H. Adams. 

 [Hiiiiclla Ads., i860, not Dallas, 1854.) Recent, Amazon River. 



Section AiiisorJiynch-iis Conrad. 



Valves subequal, smooth or concentrically undulated, the shell rounded 

 and inflated in front, prolonged into a long rostrum behind, with an escutch- 

 eon-like area defined by two dorsal keels behind the beaks; hinge and other 

 characters like Corbula. Type Corbula pyriformis Meek. Brackish-water 

 Tertiaries of Montana. 



Section Erodona Daudin. 



Shell elongate triangular, feebly concentrically sculptured with a coii- 

 spicuous epidermis, the left umbo superior, though the left valve is not the 

 larger; hinge of a strong, nearly vertical process supporting the resilium, 

 with a small socket on each side in the left valve ; in the right valve a deep 

 central pit for the resilium, the edges of the hinge-plate bordering it turned up 

 on each side as a narrow projection fitting into the sockets opposite, but no 

 well-defined cardinal tooth or laterals ; the ligament is obsolete. Type Mya 

 labiata Maton, from Brazilian estuaries. Potamoinya Sby., 1S35, and Azara 

 Orbigny, 1839, are synonymes. 



Section Botlirocorbiila GalolD. 

 Shell ovate, solid, pointed behind ; valves similarly sculptured with strong 

 concentric ridges ; lunular region impressed, sometimes forming a globular 

 cavity in the hinge-margin; shell otherwise like Qtneocorbula. Type Corbula 

 viminca Guppy. Oligocene to recent in the Antillean region. 



