362 NORTH AMERICAN INDEX FOSSILS. 



XXXIX. Pachydomella Ulrich. 



Shell extremely ventricose; valves thick and strong, the left 

 much the larger, its thick edges overlapping those of the right 

 valve all around ; dorsum arched, ventral edge more nearly straight, 

 ends rounded, a faintly impressed subcentral spot present. De- 

 vonic. 

 100. P. tumida Ulrich. (Fig. 1665,3/,^.) Devonic. 



Shell deeper than high ; right valve smaller and more ventri- 

 cose. (Type of genus.) 



Bryozoan bed (Onondaga) of Falls of Ohio. 



XL. Krausella Ulrich. 



Elongate ; dorsal margin curved, ventral nearly straight ; valves 

 unequal, the left overlapping the right both dorsally and ventrally ; 

 a single spine occurs on each shell, this being a prolongation of 

 the posterior extremity of the smaller (right) valve. Genotype 

 K. incequalis Ulrich. Ordovicic, perhaps Siluric. 

 loi. K. arcuata Ulrich. (Fig. 1667, a-^:.) Ordovicic. 



Valves moderately convex; spine blunt, anterior end sharply 

 rounded. 



Stones River of Minnesota, Cincinnati region and Tennessee. 



XLI. Entomis Jones. 



Shell subovate, fabiform or subreniform ; valves with a slightly 

 curved, submedian vertical furrow beginning near the center and 

 increasing in strength to the hinge line; in front of the furrow 

 occasionally a rounded tubercle. Surface marked generally with 

 raised concentric, transverse or longitudinal lines. Genotype E. 

 tuberosa Jones. Ordovicic-Carbonic. 



Numerous species, some of them probably not congeneric, have 

 been referred to this genus. E. serrato-striata Sandburger, the 

 best known species of the genus is extremely abundant in the 

 Upper Devonic of Germany and England. 



102. E. madisonensis Ulrich. {¥\g.i66y,r,s.) Ordovicic. 



Ends regularly rounded ; sulcus narrow and rather deep ; no 

 pronounced tubercle. 



Upper Cincinnatian of Indiana. 



