AND OTHER FAMILIES. 33 



Cabinet of Professor Ravenel, Charleston, S. C. 

 Cabinet of P. H. Nicklin. 

 Cabinet of Professor Vannxem. 

 Diam. -7, Length -9, Breadth 1-5 inches. 



Shell widely ovate, oblique, inequilateral, subangnlate posteriorly, 

 slightly inflated, compressed at posterior and inferior margins ; substance 

 of the shell tliick and white anteriorly, thin and iridescent posteriorly; 

 ligament short and thick; epidermis dark brow^n and finely wrinkled; 

 cardinal tooth short, thick and deeply divided in the left valve, single 

 and rising from a pit in the right valve ; lateral teeth oblique, straight 

 and thick, having a direction over the lateral tooth ; anterior and pos- 

 terior cicatrices both distinct; dorsal cicatrices situated within the cavity 

 of the shell on the plate between the cardinal and lateral teeth ; cavity 

 of the beaks shallow and rounded ; nacre white in the anterior, and 

 iridescent in the posterior portion. 



Remarks. — This shell, which I owe to the kindness of Professor 

 Ravenel, has, I believe, been first noticed by that gentleman, who, sup- 

 posing it to be new, sent it to me about a year since. It differs in its 

 outline from any of our eastern species, as it does also in its obliquity. 

 In these characters it most resembles the U. patulus (nobis) ; it is, how- 

 ever, more dilated, — in some specimens the margin being subrotund. 

 The only specimens obtained by Professor Ravenel being imperfect, 

 and much eroded at the beaks, I have not described that part, leaving 

 it for future observation. There are no rays to be observed on the 

 specimens I have. In young or fine specimens, it is very possible they 

 may exist. 



Unio MuRCHisoNiANus. Plate III. fig. 6. 



Testa angvlato-elllpticd, t)-unsverscl, inrnquilateraU, vahulis ienuicuUs ; natibits 

 perplicalis ; dcntibus cardlnalibus in valvuld utruque dtiplicibtts, lateralibus rectis ; 

 margaritd pulchrd, iridescenle, et salmonis colore subtinctd. 



Shell narrow-elliptical, transverse, inequilateral; valves rather thin; beaks much 

 VOL. v. — r 



