554 Contributions to Invertebrate Paleeontology. 



the crinoid. The summit arms have been small but proportionally strong at 

 the base, the earlier series of plates only being preserved. 



The surface of the plates has been elevated in the middle and perhaps ridged 

 in a stellate manner, but they are too small and too much weathered to allow 

 of a perfect detenni nation of this feature. The centre of the radial series is 

 elevated so as to form a distinctly marked ridge traversing the series from and 

 above the third radial ; while the first and second radials bear short obtusely 

 rounded spines, of a length somewhat greater than the diameter of the plate. 

 The spines of the first radials project outward and downward at an angle of 

 nearly forty-five degrees to the line of the base, while those of the second 

 radials are a little inclined below a horizontal. 



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 difference. It agrees so nearly in all the details of struc- 

 ture in the permanent 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 summit arms 

 there may have been distinguishing- characteristics, but in their 

 absence I should prefer not to name it as a different species from 

 that one. 



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

 at Smith and Price's quarries, near Columbus, Ohio. Hyatt Bro- 

 thers, collectors. 



MOLLUSCOIDEA. 

 BRACHIOPODA. 



Genus SPIKIFEKA Sowerby. 



Spirifera ziczac. 



Plate XI, fig. 13. 



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

 Spirifera 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 

 imperfect condition, being single valves preserved in a limestone 

 matri.x, 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 bottom of the sinus of the ventral valve is 

 sufficient to fully characterize them as belonging to this species. 



