28 PROCEEDINGS OF THE ACADEMY OF 



to see Dr. Morton's original specimen, but, judging from his figures and a 

 carefully drawn sketch of its hinge sent us by Mr. Gabb, it seems to us more 

 nearly allied to Cypricardia of Lamarck than to Cyprina. 



The only question in regard to the propriety of retaining Dr. Morton's name 

 arises from the fact that it had been previously (1829) applied by Duponchel 

 to a group of lepidopterous insects. If Dupouchel's genus is a good one, we 

 think Morton's name for the group of shells to which the species under con- 

 sideration belongs should be changed, although we are aware many natural- 

 ists are inclined to admit the use of the same generic names in different de- 

 partments of Natural History. 



Locality and position. Same as preceding. 



Genus PHOLADOMYA, Sowerby. 

 Pholaoomya papyracea. 



Shell rather under medium size, extremely thin and fragile, transversely 

 subovate in outline, moderately convex in the anterior and umbonal regions, 

 cuneate and a little gaping behind ; outline of base regularly semiovate, its 

 most prominent part being somewhat in advance of the middle ; anterior side 

 short and rounded ; posterior margin more narrowly rounded ; hinge margin 

 straight, long, not inflected so as to form a distinct escutcheon ; beaks mode- 

 rately gibbous, rising little above the hinge, incurved and located near the 

 anterior extremity of the shell, but not terminal. Surface ornamented by 

 about twelve small radiating costse, which are interrupted by numerous small, 

 regularly arranged concentric ridges. The radiating costse are divided by the 

 concentric ridges, so as to present the appearance of rows of minute nodes 

 placed upon the latter. The surface markring are all distinctly impressed 

 upon the internal cast. 



Length, 1*16 inches ; height, 0*76 inch ; breadth or convexity, 0-55 inch. 



This species seems to be closely allied to Pholadomya occidentalis of Morton, 

 (Synopsis Org. Rem. pi. viii. fig. 3,) but is much smaller, and differs in having 

 numerous regular concentric ridges, separated by furrows that completely 

 divide the radiating costse, which are less numerous and more regularly 

 arranged than on Morton's species. 



It also resembles P. ovulum of Agassiz, (Etud. Crit. sur les Moll. Foss. tab. 

 36, fig. 1 6,) an Oolitic species, but has a longer and straighter hinge margin, 

 and differs in being destitute of a distinctly defined depression along the 

 dorsal margin. Its concentric ridges likewise appear to differ in being more 

 regular and distinct. 



Locality and position. Same as preceding. 



Monograph of the Species of SPH2ERIUM of North and South America. 



BY TEMPLE PRIME. 

 (Continued from page 409, Dec, 1861.) 



15. Sph. triangulare, Say. 



Cyclas trianyularis, Say, New Harm. Dissem. 356, 1829. 



Animal not observed. Shell transversely oval, nearly equilateral, rather 

 full, anterior margin slightly distended, rounded, posterior somewhat abrupt, 

 nasal rounded ; beaks large, full, prominent ; lines of growth regular, epi- 

 dermis brownish ; hinge margin narrow, curved ; cardinal teeth very distinct, 

 assuming the shape of the letter V reversed ; lateral teeth prominent. 



Long. 9-16 ; lat. 7-16 ; diam. 4-16 inches. 



Hah. N. America, in Mexico. (Cabinet Acad. Nat. Sci. Philada.) 



The specimens from which I have prepared this description were presented 

 to the Academy of Natural Sciences of Philadelphia by Mrs. Say, as the Cyclas 



[Feb. 



