NKW LINIONID.I-; 01' THK UNITED STATES. 97 



more transverse than the former and less so than the latter. None of the beaks were 

 perfect, but .there were evidently two or three rugose undulations on one of the 

 specimens. 



fTxiO fFCU!!. Pi. \?,, fig. 241. 

 Testa hcvi, ublougii, subiuflata, aj latere subplanulata, po.stiee rotuudata, valde inacfiuilalcrali ; valvuli.s 

 tenuibus, subdiaphanis; natibus subpromincntibus, ad apices undulatis; epidermide olivace.T, eradiatfi ; 

 dentibus cardinalibu.s parvissiniis, comprcssis subrectLsque ; lateralibus longis, practenuis, lamellatis sub- 

 rectisquc ; iiiargarita cwrulea ct valde iridc.<ccnte. 



Shell smooth, oblong, somewhat inflated, flattened at the sides, rounded before 

 very inequilateral; valves thin, semi-transparent; beaks somewhat prominent, undu- 

 late at the tips ; epidermis olivaceous, without rays ; cardinal teeth very small, com- 

 pressed and nearly straight ; lateral teeth long, very thin, lamellar and nearly straight; 

 nacre blui.sh white and very iridescent. 

 Proc. Acad.ifat. Sci. 1861, p. 39. 



//a?,._Little Ocmulgee Eiver, Georgia. S. W. Wilson, M. D. 



My cabinet and cabinet of Dr. Wilson. 

 Diam. -G, Length 1, Breadth IS inch. 



Shell smooth, somewhat inflated, slightly flattened at the sides, rounded behind and 

 very inequilateral ; substance of the shell rather thin and semi-transparent ; beaks 

 somewhat raised and rather coarsely undulate at the tips ; ligament very thin, 

 rather long and light brown ; epidermis olivaceous, without ray.s, not shining, with 

 rather close lines of growth ; umbonial slope raised and very obtusely angular ; posterior 

 slope rather broad, subelliptical, carinate, with three obscure lines on each valve ; 

 cardinal teeth very small, compressed and nearly straight ; lateral teeth long, very 

 thin, lamellar and nearly straight; anterior cicatrices distinct, rather large and slightly 

 impressed ; posterior cicatrices confluent, rather large and very slightly impressed ; 

 dorsal cicatrices placed in the centre of the cavity of the beaks, but scarcely percep- 

 tible; cavity of the shell rather deep and wide; cavity of the beaks rather .shallow 

 and rounded ; nacre bluish white and very iridescent. 



Remarks. — A single specimen only, and without the soft parts, is before me. In 

 outline it is very near to inimtatus (nobis), the dorsal and basal margins being nearly 

 parallel. The f»rm of the teeth is very nearly the same also. It may, however, 

 easily be distinguished from that species. It is a smaller and much thinner species, 

 and has much more delicate teeth. The color of the epidermis differs very much, 

 inusitatus being of a reddish brown and bright, while cieur is olivaceous and dull, 

 having no brightness. It differs essentially too in not having the C(mstriction of the 

 middle of the valve which is so remarkable in invsitaivs. 



