INSTITUTE OF SCIENCE, PHILADELPHIA. 119 



another; dorsal (hinge) line not much more than half the length of 

 shell ; anterior border projecting forward basally ; posterior border 

 acutely angulated with the base ; beaks anterior, not very prominent, nor 

 very widely separated ; ligamental area narrow ; teeth almost obsolete 

 in the middle of the hinge-line, becoming oblique toward either 

 extremity ; interior of shell deep ; external surface closely ribbed, the 

 ribs strongly imbricated by the rugose lines of growth ; ribs most 

 prominent on the posterior slope, where they are echinated. 

 Length, 1.7 inch; height to top of umbo, one inch. 



Leda flexuosa, nov. sp. Fig. 66. 



Shell subequal, the posterior portion somewhat the longest ; basal 

 margin evenly rounded, not sinuous ; posterior or ligamental slope 

 feebly arched, nearly direct ; teeth crowded, v-shaped ; external surface 

 covered with concentric, not very fine, lines, which are gently angulated 

 and flexed on the posterior slope. 



Length, .55 inch; height, .25 inch. 



This shell most nearly resembles the recent Leda costdlata of 

 Sowerby, but differs from that species in the non-flexed basal outline, 

 and in lacking the very pronounced angulation of the concentric lines on 

 the posterior slope. From L. acuta it differs in the comparative coarse- 

 ness of its ornamentation, its larger size, and the posterior flexion in its 

 lines. 



Lithodomus, sp.? 



Two casts, very much like L.iiiflatiis or L. corrugatus. 



\ Lima scabra, Born. 



Mus. Caes., p. no. 



Two valves which are undistinguishable from the less spinose variety 

 of the recent species inhabiting the West Indian seas. The echination 

 is very fine, appearing somewhat like a raised tessellation. Possibly 

 this form may represent a variety of the East Indian L. tcnera, of 

 Chemnitz. 



List of Species occurring in the Miocene deposits of Ballast Point, 



Hillsboro Bay. 



Wagneria pugnax, Turbo heliciformis, 



Murex larvaecosta, Delphinula (?) solariella, 



" crispangula, Pseudotrochus turbinatus, 



" tritonopsis, Cerithium precursor, 



" trophoniformis, Potamides (Pyrazisinus) campanu- 

 " spinulosa, latus, 



Latirus Floridanus, Partula Americana, 



