248 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



interradial depressions, surrounded by small nodose plates of rather irregular 

 arrangement. Orals tuberculous ; anus excentric. 



Horizon and Locality. — Hamilton group ; Ontario Co., and Thedford, 

 Ontario. 



Types in the New York State Cabinet of Natural History at Albany, and 

 in the Canada Survey Museum at Ottawa. 



THYLACOCRINUS Oehlert. 



1878. Oehlert; Extr. du Bull. Soc. Geol. de France (ser. 3) Tome YU., p. 578. 



1879. Zittel; Haiidb. d. Palaiont., Yol. L, p. 375. 



1881. IV. and Sp. ; Bevision Palseocr., Part II., p. 207 (Proceed. Acad. Nat. Sci., Pliila., p. 381). 



Calyx large, plates convex; anal interradius distinct from the others; 

 arms arranged in groups of four or more. Infrabasals ^\e, small. Basals 

 fi\e, heptagonal ; their upper faces truncated, and each plate supporting an 

 interradial. Eadials followed by two costals, and these by 2X2 distichals, 

 which in turn support within the calyx several brachials of a third, and 

 sometimes of a fourth order. Arms heavy, long, simple throughout, and 

 biserial. Interbrachials numerous, arranged longitudinally in series of two 

 or three, with additional plates at the anal side. Interdistichals very numer- 

 ous, in rows of one or two ; interpalmars also represented. Construction of 

 the tegmen and position of the anus unknown. Column, so far as observed, 

 pentangular with re-entering angles. 



Distribution. — Devonian ; France, and Hamilton group ; Western New 

 York. 



Type of the genus. — Thjlacocrinus Yannioti Oehlert. 



Remarks, — Thylacocrinus differs from RJiodocrinus in having interdis- 

 tichals and interpalmars; the former being very rarely, the latter never, 

 preserved in that genus. It also differs in the arrangement of the plates 

 of the anal side, in having four or more primary arms to the ray in place of 

 two, and in that the arms are large and simple throughout. 



Thylacocrinus Clarkei W. and Sp. (nov. spec), 



Plate XIII. Figs. 11a, h. 



Calyx apparently globular ; the plates very gradually and uniformly de- 

 creasing in size upwards. Infrabasals small, and forming a pentagon with the 

 points of the angles slightly projecting beyond the column; column attach- 



