tRENTON LIMESTONEi 115 



152. 15. LEPTiENA TENUILINEATA. 



Pl. XXXI. B. Fig. 8. 

 Strophomena tenuilineata. Conrad, Jour. Acad. Nat Sci. Philadelphia, 1842, Vol. viii. p. 259. 



" Semioblong-oval, with minute crowded radiating lines ; cardinal extremities slightly 

 salient and angulated ; one valve slightly convex, the other flat. 



" Distinguishable from its congeners of the Trenton limestone by the slight convexity of 

 the inferior valve, and the extreme fineness of the radiating lines. The outline is also 

 different, being wider at the base than any other Trenton species. It resembles Orthis 

 compressa (Sowerby), except in outline being much longer in proportion to the width. 



" Occurs in Trenton limestone." 



The above is quoted from Mr. Conrad's description and remarks, not having seen the 

 shell myself. The drawing is given from his figure, marked with this name, and is doubtless 

 correct. It is evidently a rare species, as I have never met with a single individual. The 

 Orthis compressa of Sowerby, to which Mr. Conrad compares this species, is a Lower 

 Silurian fossil, corresponding very nearly in position to this one. 



153. 16. LEPTiENA SUBTENTA. 

 Pi.. XXXI. B. Figs. 9 a, b. 

 Strophontena tubtentd. Conbao, MS. and figure. 



Resupinate, semioval ; ventral valve convex in the middle ; cardinal extremities deflected, 

 somewhat abruptly curving towards the margin, and flattened on the umbo ; surface marked 

 by fine equally bifurcating striae, which are crenulated by concentric lines, obliquely 

 wrinkled on the cardinal margin ; interior of the hinge showing tWo projecting toothlike 

 processes, with a narrow space between them for the passage of a ligament ; lateral teeth 

 spreading widely. 



I find, among the drawings of Mr. Conrad, the figure of a Trenton species, with this 

 name attached. I have not seen the same in New- York, but the specimen figured is from a 

 western locality. It bears all the essential marks of the species cited, and I have therefore 

 introduced it under that name. It will, doubtless, be found again in New- York. The 

 cardinal margin bears some resemblance to Chjitetes, but a careful examination does not 

 show any spires. The strong obliqtie wrinkles form a distinguishing feature. 



Fig. 9 a. View of the dorsal valve. 

 Fig. 9 b. Interior of the hinge margin. 



Position and locality. In the Blue limestone of Ohio, associated with Leptana alternata^ 

 L. sericea and Orthis testudinaria. Oxford ( Ohio). Trenton Falls, on the authority of Mr> 



CoNRADt 



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