110 
PALEONTOLOGY OF NEW-YORK. 
146. 9. LEPT/ENA SERICEA.* 
Pl. XXXI. B. Figs. 2 a, b, c, d, e,f, g, h. 
Leptccna sericea. Sowerby in Sil. Researches, 1S39, pag. 03G, pi. 19, fig. 1. 
Leptcena semiovalis. Conrad, Ann. Geol. Report, 1838, p. 115. 
Stropho7ncna sericea. Id. Ib. 1840, p. 201 ; 1841, p. 37. 
— — Emmons, Geol. Report, 1842, pag. 394, ill. 105, fig. 1. 
Semioval ; length usually somewhat more than half the width on the cardinal line ; 
cardinal line extended a little beyond the sides of the shell ; dorsal valve convex in the 
centre, deflected at the edge ; ventral valve concave (nearly flat, Sow.); surface marked 
by fine striae, which are even and uniform, or alternating with stronger ones ; striae in¬ 
creasing in number towards the margin, granulate or papillose, crossed by a few lines of 
growth ; surface shining. 
This beautiful and abundant little shell is readily distinguished by its almost perfectly 
semioval form, with fine papillose striae alternating with larger ones ; the latter are often 
obsolete, and the surface appears uniformly striated. 
Fig. 2 a, b. The form and surface of the shell are perfectly preserved in this specimen, both valves of 
which have distinct larger striae alternating with several smaller ones. 
Fig. 2 c, d. The opposite valves of another specimen, showing equal striae and a few concentric lines of 
growth. 
Fig. 2 e. The interior of the ventral valve, showing two winglike papillose callosities for the visceral 
attachment; these are separated by a deep groove in the centre, and margined on that side 
by a sharp elevated ridge. This marking presents some slight variations of form, sometimes 
apparently from having been worn, and in others there appears to have been some original 
difference. 
Fig. 2/ shows a variation from the preceding internal structure. 
Fig. 2 g. Interior of the convex valve, showing the visceral impression, margined by a sharp elevated 
ridge, which converges to the deltoid opening in the area. 
Fig. 2 h. View of the cardinal area of the convex valve, showing the deltoid aperture which is partially 
closed. 
From the great numbers of the separated valves of this species, the internal structure can 
be well examined. A large part of the interior surface is marked by elevated points, as if 
for the attachment of muscles. The exterior is also papillose, and, where partially ex¬ 
foliated, the surface is shining and strongly punctate. 
* I have adopted, in this case, Mr. Sowerby’s name, though apparently in opposition to the rule by which I intended 
to be governed ; but notwithstanding Mr. Conrad’s name has precedence in point of time, it was not accompanied by 
any description or figure, while that of Mr. S. has both. I have, in all cases where possible to ascertain what shells 
were intended by Mr. Conrad, applied his names, or given them as synonyms, in order to show what species were 
indicated by him in his Annual Reports. This is but justice to Mr. C.; and any error or failure must be chargeable 
only to my inability to identify the species, since there are few labelled specimens in the Collection of the State at this 
time. 
