282 THE CEINOIDEA CAMEEATA OP NOETH AMEEICA. 



disk flat • composed, so far as observed, of very minute; irregular pieces, 

 apparently without oral plates. Anus excentric, opening out directly through 

 the tegmen. Column round ; axial canal of medium size, and obtusely pent- 

 angular. 



Distribution. — Upper Silurian of America, England, and Sweden. 



Bemarks. — Hall in proposing this genus made " Mariacrinus " nohilissimiis 

 the type of a genus, which in all essential characters agrees with Melocrinus 

 Goldf , notably in the arm structure ; the arms being given off from the 

 sides of tubular appendages. Among the species referred by Hall to Maria- 

 crinus were some with a very different arm structure, and in 1881 we recon- 

 structed the genus with Mariacrinus jjhmosus and M. Carleyi as types. The 

 genus, as we proposed it, includes only those species with four basals in 

 which the arms are given off directly from the calyx. 



Zittel regards Mariacrinus^ as typified by M. nobilissimus^ as a synonym of 

 Ctenocrimis Bronn, in which we agree ; but the latter genus, according to 

 Schultze, ^ is identical with Melocrinus, 



Mariacrinus macropetahs Hall is probably a Corymlocrinus Angelin ; Maria- 

 crinus stolonifenis Hall is described from fragmentary columns. Glt/j^tocriniis 

 Harrisi S. A. Miller, which we erroneously referred to Mariacrinus, not 

 knowing it had an anal plate between the radials, has been transferred to 

 Compsocrinus . Mcwiacrinus granulosus S. A. Miller is too fragmentary for 

 identification, but certainly belongs to a very different group. 



Mariacrinus Carleyi (Hall). 

 Plate XXII. Figs. 2a, h, c. 



1863. Qlyptocrinus Carleyi-— TIa.-ll; Trans. Albany Inst., Vol. IV., p. 203; also 28tli Eep. N Y. State 



Mus. Nat. Hist., 1875, p. 133, Plate 14, Figs. 7-10. 

 1881. Qlyptocrinus Carleyi — Hall; lltli Ann. Geol. Rep. Indiana, p. 261, Plate 13, Pigs. 7 to 11, and 



Plate 15, Pig. 5. 

 1881. Mariacrinus Carleyi — W. and Sp. ; Revision Palseocr. Part II., p. 116. 



Calyx obconical, higher than wide; the sides distinctly convex, section 

 across the costals sharply pentagonal, and across the distichals decagonal ; 

 the radials marked by very prominent rounded ridges ; the interradial spaces 

 depressed. Narrower and more angular ridges pass out to the sides of the 

 radials, where they meet with others from the interbrachials, dividing the 

 surface of the dorsal cup into numerous triangular depressed areas, which 



* Monogr. Echinod. Eifler Kalk., p. 61. 



