448 GEOLOGY OF OHIO. 



I had at first described this as a distinct species from the New York 

 form, on account of the less depressed interradial areas, but on more 

 critical comparison have decided that this may be only an individual dif- 

 ference. It agrees so nearly in all the details of structure in the perma- 

 nent features of the crinoid, that it does not seem possible to point out 

 any distinguishing features that can be called specific. It is true that in 

 the details of the true and the summit arms there may have been distin- 

 guishing characteristics, but in their absence I should prefer not to name 

 it as a different species from that one. 



Formation and Locality. — In limestone above the " Bone-bed," at 

 Smith and Price's quarries, near Columbus, Ohio. Hyajt Brothers, col- 

 lectors. 



MOLLUSCOIDEA. 



BRACHIOPODA. 



Genus SPIRIFERA Sowerby. 



Spirifera ziczac. 



Plate VII, fig. 13. 



Dethyris ziczac Hall, Geol. Rept. 4th Dist. N. Y., 1843, p. 200, fig. 5. 

 Spirijera ziczac Hall, Pal. N. Y., vol. 4, p. 222, pi. 35, figs. 15-23. 



The specimens of this species recognized in Ohio are in a very imper- 

 fect condition, being single valves preserved in a limestone matrix, and 

 consequently much exfoliated when detached from the rock. Enough, 

 however, remains to show the strongly lamellose structure of the surface, 

 which together with the form of the shell and the mesial rib in the bot- 

 tom of the sinus of the ventral valve is sufficient to fully characterize 

 them as belonging to this species. 



The form of the ventral valve is somewhat triangular, much wider 

 than high, the beak somewhat prominent and extended beyond the line 

 of the hinge; body of the valve ventricose and strongly arcuate, with a 

 deep, moderately wide mesial sinus, the bottom of which is occupied by 

 a slightly elevated rib, corresponding to the depression in the fold of the 

 dorsal side; from eight to ten angular ribs occupy each side of the valve; 

 cardinal area moderately high and incurved, foramen nearly as wide as 

 ..high. Surface of the shell marked by strong, concentric, lamellose 

 lines. 



Formation and Locality. — In the blue limestone layers above the 

 "fish-beds" at Delaware, Ohio. 



