LOWER SILURIC SHALES OF THE MOHAWK VALLEY 99 



Clidophorus foerstei nov. 



PL 5, fig. 15, 16 



Hall (title 3, page 301) cites C. planulatus (Conrad) as 

 occurring besides in the Lorraine beds- of northwestern New York, 

 also in the altered slates of Waterf ord, Saratoga county, N. Y., 

 and figures a specimen from that locality (op. cit. plate 82, fig- 

 ure 9e). We have in our earlier work (Bulletin 42) followed that 

 authority in identifying the Clidophorus from the shales of the 

 Hudson valley with the Lorraine form. The better preserved 

 material since obtained at Snake hill has shown however that there 

 are at least two species of this genus present in the Snake Hill beds, 

 one of rather ventricose form, here described as C . v e n t r i - 

 c o s u s , and another that comes near to C. planulatus. 

 Hall's above-cited type from Waterford belongs to this second 

 species. As his own figure shows this species is also more ventri- 

 cose than the C. planulatus although approaching it closely 

 in general outline. By a careful comparison of the Snake Hill speci- 

 mens with types of C. planulatus from the Lorraine beds, 

 we have ascertained the following dififerences : the shell of 

 C. foerstei is less elongate, or relatively higher, in 

 C. planulatus the length being two to two and one-half 

 times greater than the height, and in C. foerstei somewhat 

 less than two times greater ; while in the former species the ventral 

 slope is very flat, and the shell much compressed, as expressed in 

 the name; that of C. foerstei is more convex, although not 

 nearly so as in C . v e n t r i c o s u s ; the clavicle is decidedly 

 shorter in C. foerstei. 



Horizon and locality. Snake Hill beds at Snake hill, Saratoga 

 county, and other localities of that formation in Saratoga and 

 Albany counties. 



Clidophorus ventricosus nov. 



PI. 5, fig. 11-14 



Description. Shell of medium size for the genus or above ; trans- 

 versely subrhomboidal in outline; subalate ; with the height a little 

 more than one-half the length of the shell, anterior end rounded and 

 narrower than the posterior one which is obliquely truncate; the 

 ventral margin is rather strongly convex and the dorsal margin 

 straight posteriorly of the beak and declining obliquely forward in 

 front of the beak. The posterior dorsal and posterior ventral 



4 



