158 PALJ^OXTOLOGY OF OHIO. 



CRINOIDS OF THE GENE«SEE SLATE AND CHEMUNG 



GROUP. 



The two following species of Crinoids are of considerable interest 

 from their supposed geological position, coming from formations which 

 have heretofore yielded so few forms of this class. The Platycrinus is 

 from rocks which are probably equivalent to the Chemung or Portage of 

 New York, while the other is from beds supposed to be of a correspond- 

 ing age with the Genessee Slates of New York, a formation that has 

 never jdelded any remains of Crinoids within the limits of that State. 



Genus MELOCRIN'US, Goldf. 



Sub genus CTENOCRINUS, Brown. 



Melocrinus (Ctenocrits^us) Bainbridgensis (n. sp.). 



Plate 13, figs. 2 and 3. 



Body rather above a medium size, very broadly turbinate, spreading 

 somewhat rapidly from the base to the origin of the free arms, strongly 

 pentangular in a basal view; dome low pentapyramidal, the highest 

 point nearer to the largest interradial (anal) area, the summit perforated, 

 and has apparently been surmounted by a very small or slender pro- 

 boscis ; spaces above the interradial areas somewhat depressed, the whole 

 composed of small polygonal plates, apparently without definite arrange- 

 ment, except in the depressed areas, where they are indistinctly ar- 

 ranged in transverse lines. The four basal plates form a low vertical 

 rim at the base of the cup, which is slightly lobed by the depression of 

 the suture lines. First radial plates large, a little wider than high, four 

 of them heptagonal, the other hexagonal ; second radials hexagonal, 

 wider than high, the widest part mostly above the center of the plate ; 

 third radials smaller than the second, but variable in size and form. In 

 the specimen used for description they are heptagonal in the anterior 

 ray, and hexagonal in the left p^stero-lateral ray, while in the other 

 three they are pentagonal. The supraradials are arranged above the 



