no PAt^ONTOLOGY OF NEW-YORK. 



146. 9. LEPT^NA SERICEA.* 



Pl. XXXI. B. Figs. 2 a, b, c, d, e,f, g, h. 



Leptcena serieea. Sowerby in Sil. Researches, 1839, pag. 63t), pl. 19, fig. 1. 

 Lejitcena semiovalis. Conrad, Ann. Geol. Report, 1S38, p. 115. 



SIrop/wmena serieea. Id. lb. 1S40, p. 201 ; 1S41, p. 37. v, 



_ — 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 ; strise 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 strife alternating with larger ones ; the latter are often 

 obsolete, and the surface appears uniformly striated. 



Fig. 2 a, h. The form and surface of the shell are perfectly preserved in this specimen, both valves of 

 which have distinct larger striaj alternating with several smaller ones. 



Fig. 2 c, d. The opposite valves of another specimen, showing equal strife 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 f, 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. Sowkrby'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 oi' 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 rhargeable 

 only to my inability to identify the species, since there are few labelled specimens in the Collection of the State at this 

 time. 



