160 



PALEONTOLOGY OF OHIO. 



nating; every fourth plate on each side is thickened on the outer end, 

 and supports an armlet, which is composed of a single range of short, 

 flat plates, supporting tentaculse, the precise nature of which can not be 

 satisfactorily made out in the fragment under examination. The armlet- 

 bearing plate of the right side of the arm rests immediately upon that 

 bearing an armlet on the opposite side of the arm, leaving three simple 

 plates between this and the next armlet below. 



The species bears considerable resemblance to Melocrinus breviradiatus 

 (name issued with explanation of photograph plate, August, 1872), from 

 the Hamilton group of New York, but difl'ers in the less projecting rim 

 at the base of the cup, formed by the basal plates, in the greater inequal- 

 ity of the interradial and anal areas, and also in the surface character 

 and ornamentation of the plates, as well as in the flattening of the sur- 

 face of the plates themselves, those of that species being highly convex, 

 approaching tumidity. 



The form of the arm bases, together with the character of the arm 

 found associated with it, would indicate the existence of only a single 

 strong arm to each ray, bearing numerous armlets along its sides. This 

 feature is the one peculiarity of the genus Ctenocrinus, Brown, as exem- 

 plified in 0. stellaris, Roemer (Pictet's Traite de Palaeont., PI. CI., fig. 1), 

 and to which this fossil, in its structure, bears a striking resemblance, 

 difiering only in the possession of four basal plates, which are strongly 

 marked and positively divided in this species, although somewhat more 

 obscure in M. (0.) breviradiatus, which appears to be congeneric, while in 

 the generic description given in Bronn's Lethea, the number of basal 

 plates is said to be only three; but still there seems to be some doubt 

 about it, as the number is followed by an interrogation point. The 

 principal feature, however, claimed for the generic distinction being the 

 form and number of the arms, and the arrangements of the armlets, we 

 prefer to place this species under the genus, believing that the C. stellaris, 

 when thoroughly examined, will prove to possess four basal plates. This 

 form of structure will make it in all respects, as far as the body is con- 

 cerned, the same as in Melocrinus, Goldf. The Melocrinites nodosus. Hall 

 (Kept. Progr. Geol. Surv. Wisconsin, 1861, p. 19), will probably also prove 

 to belong to this same division of the group. 



Formation and locality : In a limestone layer, sis inches in thickness, about thirty feet 

 above the base of the Huron Shales (Black Slates), Bainbridge, Ross county, Ohio. 

 Ohio State collection. Collected by Mr. J. H. Poe, of Chillicothe, Ohio. 



