FOSSILS OF THE HUDSON EIVEK GROUP. 69 



sibility of its being a true Lingula ; and the strona; mesial ridge along 

 the interior of the valves would seem to separate it entirely from the 

 former genus. But as the material now in hand is not entirely satisfac- 

 tory, we prefer to refer it to Lingulella, as we are not certain in what par- 

 ticulars it may differ from the genus Dignomia. 



Formation and locality: In the shales of the Hiulson River group, at Cincinnati, 

 Ohio. Collection of U. P. James, Esq. 



Genus LEPTOBOLUS, Hall. 

 Leptobolus lepis. 



Plate 1, figs. 10, 11. 



Leptololus lepis, Hall; Descr. of New Species of Fossils from Hud. Riv. Gr., etc., Oct., 



1871, p. 3. 

 Leptobolus lepis, Hall; 24th Eept. State Cab., p. 226, pi. 7, figs. 19, 20. 



"Shell minute, ovate, or broadly elliptical in outline, about three-fifths 

 as wide as long, and seldom exceeding seven hundredths of an inch in 

 length ; moderately convex, the greatest convexity about one-third of the 

 length from the beak; ventral area thickened; pedicel groove strongly 

 defined; muscular impression broad, extending more than one -third the 

 length of the valve ; muscular ridges of the dorsal valve strongly marked, 

 the central one extending two-thirds the length of the shell, the lateral 

 ones diverging from each other at an angle of about forty-five degrees, 

 and extending nearly to the middle of the valve ; extremities bifid." 



" Surface of valves concentrically marked by fine lines of growth." 



The specimens of this species are minute scale-like bodies, found scat- 

 tered over the surface of the layers in certain beds of the formation, and 

 are easily overlooked, except by those accustomed to the forms usually 

 found in the formation. They are an exceedingly interesting group of 

 shells, from the fact of their ai)parently gregarious habits, and the great 

 numbers of individuals usually found associated in localities where they 

 occur. The same habit appears to have prevailed among the other spe 

 cies of the genus, so far as yet observed. 



Formation and locality: Shales of the Hudson River group, at Cincinnati, Ohio. 

 The original specimens were from the collection of Mr. C. B. Dyer. 



