INSTITUTE OF SCIENCE, PHILADELPHIA. 97 



narrower, nor does there appear to be any marked variation either in the 

 disposition or the size of the costal. Still, the differences here indicated, 

 which are based upon figure and description only, may be more apparent 

 than real, and the two forms, as above intimated, may in reality repre- 

 sent a single species. Unfortunately for the determination of this point, 

 the only perfect valve possessed by Tuomey and Holmes was lost before 

 the publication of their monograph, and the fragment which served as 

 the type of the species, for both figure and description, and which, as far 

 as I am aware, was the only other specimen extant illustrating the 

 species, has since been lost from the collection of the South Carolina 

 geologists. I am informed to this effect by Prof. Whitfield, of the Amer-' 

 ican Museum of Natural History, of New York city, where the type 

 collections of the South Carolina Survey are deposited. 



Area lienosa, Say. 



American Conchology, pi. 36, fig. i. 

 Area Floridana (recent), Conrad. 



This shell is identical with the recent Area Floridana, from the Florida 

 coast, the specific name of which will have to be replaced by that of 

 Say's species, which has priority. The only difference that it presents, 

 and this is probably not constant, and at most a trifling character, 

 is a somewhat greater anterior projection of the hinge-line, making the 

 shell appear more distinctly eared. It does not appear, however, that 

 the recent form attains the size of that seen in the fossil ; one of the 

 specimens from the upper Caloosahatchie measures six inches in length, 

 and three inches in height to the top of the umboues. The ribs where 

 worn, especially towards the base, show a double or quadruple struc- 

 ture, best seen in the larger specimens. 



Area aquila, nov. sp. Fig. 31. 



Shell (known only by its left valve) elongated, rectangular, winged, 

 profoundly sulcated on the posterior slope ; anterior border vertical, 

 straight ; basal line slightly sinuous beyond the middle ; posterior border 

 deeply emarginated ; hinge-line straight, of nearly equal length with the 

 base ; teeth very numerous, gradually increasing in size towards either 

 end, where they are markedly oblique; hinge-area broad, obscurely fur- 

 rowed in longitudinal lines ; beak moderately elevated, incurved, the apex 

 directed backward ; surface of the shell radiately ribbed, the ribs sinuous, 

 beaded especially on the anterior portion of the shell, where they are 

 separated by an intermediate fine line becoming obsolete in the posterior 

 sulcus and on the wing, where they are represented by two pairs of lines ; 

 lines of growth prominent towards the base and on the wing ; basal mar- 

 gin crenulated. 



