302 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



three plates in the second row, and four in the third. Ventral disk depressed, 



pentagonal ; the ambnlacral regions slightly raised above the general level ; 



the plates without ornamentation, almost flat, and the sutures difficult to see. 

 The disk ambulacra are completely subtegminal; the orals apparently 



unrepresented, and the anus is at the end of a large tube, which bends 



toward the posterior side. 



Horizon and Locality. — Niagara group -, associated with Astrceos;pongia 



meniscus. Decatur Co., Tenn. 



Ti/pe in the collection of Wachsmuth and Springer. 



Remarks. — Roemer described this species as Cytocrinus IcBvis, making it 

 the type of a new genus. He supposed it had three basals, and he did not 

 understand its arm structure, which is evidently that of Melocrinus. We 

 refer the species to the latter genus, but are compelled to change the specific 

 name, as Goldfuss in 1826 described a Melocrinus Icevis from the Eifel, and 

 propose for it .Melocrinus Roemeri. Roemer originally included in his species 

 two forms, the typical one from the Niagara group of Western Tennessee, 

 and another from the same horizon of near Louisville. The latter has been 

 described by us as Melocrinus ohlongus. The two species resemble each other 

 in form, but M. oUongus is considerably larger, the calyx contains many more 

 plates, and the radial appendages are composed of two rows of brachials in 

 place of one. 



Melocrinus obconicus Hall. 

 Plate XXII. Figs. lOa, 6, c. 



1863. Melocrinus ohconicvs — ^kiil', Trans. Alb. Inst., p. 206. 



1875. Melocrinus obconicus — Hall -, 28tli Rep. N. Y. State Mus. Nat. Plist., p, 138, Plate 14, Pigs. 11-14. 



1881. Melocrinus obconicus — Ball ; lltli Ann. Rep. Geol. Ind. by Collet, p. 269, Plate 13, Pgs. 11-14. 



1881. Mariacrinus obconicus — W. and Sp. ; llevision Palseocr., Part II., p. 116. 



Of medium size. Calyx obconical, about as wide as high ; gradually 

 expanding from the top of the basals to the bases of the free appendages, 

 where it is distinctly lobed. Plates covered by numerous radiating ridges, 

 which pass out from the middle of the plates to the sides and angles, meet- 

 ing those of adjoining plates; the ridges passing up and down the radial 

 plates wider and somewhat higher. Besides these ridges the whole surface 

 of the plates — that of the ridges included — is finely corrugated, which adds 

 greatly to the beauty of the species. 



Basals projecting, forming a short, indistinctly quadrangular, almost cylin- 

 drical cup. Radials and costals of about equal size, and all nearly as long 



