FOSSILS OF THE HUDSON KIVER GROUP. 75 



The shells of this species are mostly found adhering to the surface of 

 other forms of Brachiopods, and are by no means uncommon. They gen- 

 erally assume the surface features of the body to which they are attached 

 to such an extent as to become almost unrecognizable when attached to 

 coarsely marked surfaces, and are not unfrequently mistaken for adher- 

 ing rock, and forcibly removed. When attached to shells having moder- 

 ately sized plications, the upper valve of the Crania is found to conform 

 in surface characters to that of the foreign body, the plications passing 

 obliquely across the valve, and it is only when attached to comparatively 

 smooth surfaces that the true features of the shell can be obtained. 



Formation and locality: In the shales of the Hudson Eiver group, at Cincinnati, 

 and Waynesville, Ohio, and at several other places in the same formation outside of 

 theState. 



Crania l^lia. 



Plate 1, fig. 16. 



Crania Lielia, Hall; Ext. 20th Rept. State Cab., Nov., 1866, p. 13. 

 Crania Lxlia, Hall ; 24th Rept. State Cab., p. 220, pi. 7, fig. 16. 



Shell small, discoid, or moderately convex on the upper valve ; outline 

 circular, or a little narrowed toward the cardinal border. Apex of the 

 dorsal valve minute, not prominent, varying from sub-central to about 

 one-third the length of the valve from the cardinal margin. 



Surface of the dorsal valve marked by fine but sharply elevated, radi- 

 ating strise, which are sometimes tortuous, and frequently increased by 

 implantation. Ventral valve and interior of the shell not observed. 



This is a distinct and well-marked species, not readily mistaken for 

 any other from rocks of this formation, although there are forms known 

 in higher positions that resemble it somewhat. Its nearest described 

 analogue is C. crenistria, Hall, from the Hamilton group of New York ; 

 but the stria3 are sharper and the apex more appressed. 



Formation and locality: In the Hudson River group, Oxford, Ohio. We have also 

 seen specimens from Cincinnati. 



Genus ORTHIS, Dalman. 

 Orthis clytie. 



Plate 1., figs. IS, 19. 



Orthis clytie, Hall ; 14th Rept. State Cab., p. 90, 1861. 

 Orthis clytie, Hall ; 15th Rept. State Cab., pi. 2, figs. 4 and 5. 



Shell of medium size, semi-elliptical outline, with the cardinal angles- 

 rounded; valves plano-convex; hinge line less than the width of the 



