TRENTON LIMESTONE* 
i is 
152. 15. LEPT.ENA 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. LEPT/ENA SUBTENTA. 
Pl. XXXI. B. Figs. 9 a, b. 
Strophomena subtenta. Conrad, MS. and figure. 
Resitpinate, 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 Chattetes, but a careful examination does not 
show any spires. The strong oblique wrinkles form a distinguishing feature. 
Pig. 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 Leptcena altcrnata , 
L. sericea and Orthis testudinaria. Oxford (Ohio). Trenton Falls, on the authority of Mr. 
Conrad. 
15 ; 
