96 SYNOPSIS OF THE CHARACTERS OF THE 



nian species; the ears are also different; some of the finer striaa are frequently flexuous. Length eight lines, 

 width seven and a half lines. 



Pecten leiotis. M'Coy. (PL XV. fig. 21). 



Sp. Ch. — Longitudinally obovate, subtrigonal, flat; ears'small, nearly equal, pointed, smooth; body of the 

 shell radiated with about thirty-five smooth, sharp, slender, equal ridges ; intervening spaces flat, about five 

 times the width of the ridges ; slightly wrinkled transversely. 



This beautiful shell resembles most closely the P. micropterus, M'Coy, from which it is distinguished, as 

 from most others of the radiated species, by its smooth ears. Length ten lines, width nine and a half lines. 



Pecten macrotis. M'Coij. (PI. XVI. fig. 13). 



iS/;. Cli. — Orbicular, depressed ; shghtly convex ; ears unequal ; anterior ear pointed, with strong, scaly 

 striae parallel to the margin ; posterior ear very long, acute, vsdth fine, radiating ridges, crossed by delicate lines 

 parallel to the margin, separated from the body of the shell by a steeply inclined space ; surface of the shell, 

 with about forty-nine fine, radiating, flattened ribs, rather irregular in some parts of the shell. 



This pretty species closely resembles the Pecten tabulatus, M'Coy, but is distinguished by its more orbi- 

 cular form, longer, and longitudinally striated posterior ear, the more convex body of the shell, and, finally, by 

 the much greater number of its radiating ribs. Length five lines, width six lines. 



Pecten megalotis. M'Coy. (PL XIV. fig. 7)- 



Sp. Ch. — Lengthened, ovate; ears unequal, right ear very large, falcate; surface with about twenty-three 

 narrow, radiating ribs, intervening spaces striated across ; large ear with very sharp, prominent, curved striae. 



In this species the radiating ribs are small, rounded, and rather distant, one-half only reach the beak, 

 the other half terminate at about a fourth the length of the shell from the beak ; the transverse striae are faint, 

 and rather irregular, strongest near the beak ; the large ear is marked with numerous, sharp, scale-like striae. 



Pecten meleagrinoides. If' Coy. (PL XVI. fig. 3). 



Sp. Ch. — Truncato-orbicular, convex; ears nearly equal, flattened, slightly pointed, not distinctly separated 

 from the body of the shell ; surface radiated with strong, rounded ridges, alternately larger and smaller ; the 

 interstitial spaces are about equal to the ridges in breadth, concave ; surface marked with obsolete, concentric, 

 wrinkles. 



This resembles the tuberculated valve of P. fallax, M'Coy, in shape, but is distinguished by its smoother 

 ribs, and much wider and smoother interstitial spaces ; the ears also are very different in form, resembling those 

 of a Meleu(/rina. Length ten lines, width eleven lines. 



Pecten micropterus. M'Coy. (PL XV. fig. 12). 



Sp. Ch. — Longitudinally ovate, shghtly oblique, depressed; ears very small, anterior one rectangular, 

 posterior one-third longer, acute, having a straight, flat space between it and the body of the shell ; with the 

 exception of the straight portion between the body of the shell and the posterior ear, the entire surface is ra- 

 diated with fine sharp ridges, distant about four times their diameter apart, intervening spaces smooth, with 

 obsolete, irregular, transverse wrinkles. 



This species is remarkable for the small size and singular form of its ears, besides which, it is easily known 

 from the other ancient species, by its very distant, sharp, slender, radiating ridges. Length nine lines, width 

 ten lines. 



