INSTITUTE OF SCIENCE, PHILADELPHIA. 99 



lines at intervals of about six or seven ; interior of shell deep, cunei- 

 form ; margin entire. 



Length, 5.4 inches; width across the beaks, 2.5 inches. 



Caloosahatchie, in the banks below Fort Thompson. 



Spondylus rotundatus, nov. sp. Fig. 33. 



Shell (known only by the larger valve) capacious, orbicular below the 

 hinge-line, distinctly auriculated ; hinge-line triangular, pyramidal, the 

 beak acute, laterally twisted at the apex, traversed by a median slit; 

 cartilage-pit profound, reaching about half-way to the apex ; cardinal teeth 

 powerful, slightly spreading ; external surface coarsely ornamented with 

 irregular squamous ribs and intermediate scaly fine lines, the (imbricated) 

 scales on the latter drawn out into flattened spines or echinations. 



Height to apex, 3.5 inches; greatest width, 2.5 inches. 



A solitary, perfectly preserved valve from the banks below Fort 

 Thompson. 



This species is quite distinct from any form, either recent or fossil, 

 with which I am acquainted. 



Pecten solarioides, nov. sp. Fig. 34. 



Shell suborbicular, depressed, of about equal height and width ; ribs 

 about 2O (?), quadrangular or flattened, broader than the interspaces, 

 crossed by fine rugose lines of growth ; a faint median longitudinal line 

 or carination can be detected on some of the ribs, probably eroded on the 

 others ; the interspaces with two or more elevated longitudinal lines ; left 

 ear of right valve with about five very oblique, narrow ribs, rugose with 

 the lines of growth ; right wing ? Interior of shell prominently ribbed. 



Height, 5.7 inches. 



The half of a single right valve, and a fragment of probably the other 

 valve, from the banks below Fort Thompson. 



This shell can be readily distinguished from the only species that at 

 all resembles it, Pectcn comparilis, by its more elevated form, the height 

 of its wings, and the structure and disposition of its ribs, which are more 

 distinctly quadrangular and elevated. In the fragment which possibly 

 represents the left valve the ribs are broader than in the opposite valve, of 

 about twice the width of the interspaces, which, at least in the upper 

 portion of the shell, are deep and nearly parallel-sided. They show a 

 single median elevated line. 



Pecten comparilis, Tuomey and Holmes. 



Pliocene Fossils of South Carolina, p. 29, pi. xi, figs. 6-10. 

 Pecten eboreus of Conrad (in part). 



I refer to this species a number of large Pectens, found in the banks 

 below Fort Thompson, and also at Thorpe's, some of whose forms are 



