t 



} 



Sand Ponnation of the United Stales. 245 





I 



BIVALVES. 



PLAGiosTOMA. Sowcrhy. 

 36 inches lonfi:, with num 



dinal ribs, and elevated concentric squamous plates. Is found at- 

 tached to other shells in the same way that some British species are 

 attached to flints. 



2 ? Casts are found in the marl of the Chesapeake and Delaware 

 Canal reserablbg those figured by SoAverby as P. rusticum^ pi. 381. 

 I am not certain, however, that the two fossils belong to the same genus. 



OSTKEA. 



5. About an inch long, compressed, wnth numerous diverging, spi- 



nous costae. 



:own 



PECTEN. 



3. Compressed, thin, longitudinally striated ) and bearing consid- 

 erable general resemblance to the chalk fossil P. iiitidtis of Sowerby, 

 tab. 394. 



4. A large species, found hitlierto only In fragments. Costae large 

 and convex, with a smaller one intermediate. 



CLAviGELLA. Sowcrby. 



s. 



A single specimen, apparently referrible to tliis singular genus, has 

 been found in New Jersey. 



■ 



ECHINIDE.f:. 



SPATANGUS. 



3. S. Stella. (S. 6. M.) Small, globose, with pentapetalousr 

 sulci ; the longitudinal groove does not reach to the base, in which 

 respect it differs from species 1st of diis synopsis. Common in the 

 calcareous marls. It was first pointed out to me by Mr. T 

 Peale. 



itian 



ANANCHYTES- 



2. A. cruciferus. (S. G. M.) Oval; less than an mch in lengdi: 

 apex subcentral : the two lines composing each of the five pair of am- 

 bulacra are parallel throughout; there is no sulcus. I refer this fossil 

 to ananchytes, although it does not in every respect agree w^th tliat 

 genus. Communicated by Mr. T. R. Peale. 



3- A.Jimbriatus. (S.G.M.) Four pah' of dotted ambulacra, with 

 eight or nine lines passing from the apex to the moudi, and a poste- 





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