88 SYNOPSIS OF THE CHARACTERS OF THE 



This rare and beautiful species is easily distinguished from the Devonian Pecten granulosus, Phil., witli 

 which it is alone likely to be confounded, by its very short hinge-line, and by the thickness and inequality of 

 the longitudinal striaj. Length seven and a half lines, vridth six lines. 



Lima l^vigata. M'Coy. (PL XIV. fig. 3). 



Sp. Ch. — Obliquely oval, convex; ears very small, undefined; surface smooth, with regular, obsolete, 

 concentric undulations. 



This is a very scarce species, it is regularly oval in form, the ears being so small as scarcely to interrupt 

 the regularity of the outline; the hinge -line is oblique, short; the body of the shell concentrically marked with 

 broad, rounded wrinkles or waves, which are very slightly raised above the sm-face ; to the naked eye, the sur- 

 face appears smooth, but under a lens is found to be marked with very delicate, waving, longitudinal striae. 

 Length one inch four lines, width one inch. 



Lima obliqua. M'Coy. (PI XV. fig. 7). 



Sp. Ch. — Obliquely oval, sKghtly convex, smooth, marked with few strong, distant lines of growth; 

 hinge-line very oblique. 



The obHque, regularly oval outline, together with its smooth surface, distinguishes this from the other spe- 

 cies of Lima; the lines of growth are distant, regular, and very strong. Length ten lines, width eight lines. 



Lima planicostata. 31' Coy. (PI. XV. fig. 5). 



Sp.Ch. — Obliquely ovate, compressed, hinge-line equal to the width of the shell, ears equal, distinct, 

 smooth ; surface radiated with numerous flat, unequal ribs, separated by very narrow, deep, concave sulci. 



This delicate little species is distinguishable by its broad, flat, unequal ribs, they increase in number 

 towards the margin, and are smooth ; the ears are large, the hinge-line oblique ; the beaks very small ; the 

 body is evenly, but slightly convex. Length six lines, width five lines. 



Lima prisca. M'Coy. (PI. XVIIL fig. 6). 



Sp. Ch. — Oblong, oval; hinge nearly straight; ears large, rectangular, anterior smallest ; surface with nu- 

 merous, fine, slightly undulating, longitudinal, thread-like ridges. 



This remarkable fossil bears a strong resemblance to the recent L. frag His of our coasts. The shell is 

 thin, and somewhat inflated; surface rugged transversely; from the lines of growth the beaks are small 

 but prominent, and the ears large ; the longitudinal strise sharp and distinct. Length ten lines, width seven 

 lines. 



Lima SEMisuLCATA. M'Coy. (PI. XV. fig. 2). 



Sp. Ch. — Elongate, oval, depressed ; hinge-line short, oblique ; posterior ear twice the length of the ante- 

 rior ; surface smooth, with five or six sharp, longitudinal striae in the middle of each valve. 



This beautiful Httle species is easily known by its fine, sharp, mesial ridges, all the remainder of the surface 

 being perfectly smooth, with the exception of a few, obscure, concentric wrinkles of growth. The general form 

 is rather depressed, the beak is small but prominent, the ears very short. Length seven lines, width five lines. 



Pecten. Linn. 



Gen. Ch. — Shell regular, depressed, nearly orbicular, auriculated; umbones central; ligament small, inter- 

 nal ; hinge-margin short. 



