TRENTON LIMESTONE. 97 



134. 8. LINGULA ELONGATA(n. fp.). 

 Pl. XXX. Fig. 0. 



Oblong oval, gradually narrowing towards the beak ; sides nearly straight ; shell much 

 elevated along the centre, which continues to the beak, and is slightly depressed in front ; 

 a narrow depressed line extends along the length of the shell, from the beak, more than 

 half way to the base ; surface marked by fine concentric striae, without visible longitudinal 

 ones. 



Length of the shell, ^ ; width, yV ^^ ^^^ inch. 



I have seen but a single specimen of this shell, but its great elongation, and entire 

 freedom from radiating striae, either upon the outer surface or where exfoliated, seem to 

 me sufficient marks of distinction. Our shell corresponds in many respects with Lingula 

 parallela of Phillips [ Geol. Yorkshire, Vol. ii., pi. 11, fig. 17-19), as described by 

 PoETLocK ( Geol. Report, pag. 444, pi. 32, figs. 6, 8 & 9 ) , but his specimens are much 

 smaller ; the original shell, moreover, occurs in a much higher position, which alone would 

 be a fair presumption against it being identical with the one of the Trenton limestone. 



Position and locality. In the compact dark limestone in the central part of the rock. 

 Lewis county. (Cabinet of Mt.Vasvxxm.) 



135. 9. LINGULA CURTA. 



Pi.. XXX. Figs. 6 a, ft. 

 Lingula eurta. Conrad, Jour. Acad. Nat. Science, Vol. viii. pag. 266, pi. 15, fig. 12. 



Obtusely ovate, flat or depressed convex ; beak small, often scarcely prominent ; surface 

 marked by concentric elevated lines or wrinkles ; apex obtuse ; base broadly rounded. 



The length and breadth of this shell are nearly equal, and the beak often scarcely projects 

 beyond the outline of the shell. In the Utica slate, it is quite flat from compression, while 

 in the limestone it is depressed convex. 



Fig. 6 o, is from the Utica slate, the same specimen figured by Mr. Conrad. 

 Fig. 6 b,ia from the Trenton hmestone. 



When the shell is exfoliated, fine radiating striae are visible. 



Position and locality. Middleville and East-Canada creek, in the compact dark limestone, 

 nearly in the central part of the rock. It occurs also in a higher position, and in the Utica 

 slate ; also at Carlisle ( Pa.), in Utica slate. 



[ PALiKONTOLOGT.] 13 



