BATOCEINID^. 471 



vonian of the Eifel, and there is another species at Colle, Spain, at a horizon 

 which is generally recognized as Upper Devonian. 



Type of the genus : Aorocrinus immatunis W. and Sp. 



Eemarks. — The species for which we propose the genus were referred 

 heretofore by us and others to Dorycrinus, except Aorocrinus Cassedayi which 

 had been placed under Gennceom^inns. It approaches Dorycrmus, differing 

 from it, however, in having single arms, and in not having the long spines 

 upon which Eoemer principally formulated his genus. 



Aorocrinus precedes Dorycrinus in time, and has essentially the character- 

 istics of an immature Dorycrinus. The peculiarities of that genus are fore- 

 shadowed, but have not acquired their full development. 



Aorocrinus immaturus W. and Sp. 

 Plate XL V. Figs. 4a, h. 



1890. Sorycrirms immaturus — W. and Sp. ; Geol. Rep. Illinois, Vol. VIII., p. 175, Plate 16, Fig. 5, aud 



Plate 17, Figs. 6 and 17. 

 1S90. Dorycrinus immaturus — S. A. MiLLEK ; N. Amer. Geol. and Palteont., p. 240, Fig. 290. 



Below medium size ; crown measuring from 30 to 40 mm. ; height of 

 calyx from 10 to 14, by 10 to 12 wide. Dorsal cup higher than the ventral 

 disk, gradually spreading to the arm bases, the sides a little convex. Teg- 

 men depressed conical, crowned with a subcentral elongate node or short 

 spine. Plates of the dorsal cup moderately convex, their surface more or 

 less rugose, the suture lines distinctly grooved. Color of specimens rather 

 dark. 



Basals short, somewhat projecting beyond the column, their lower ends 

 bending abruptly inward and forming a well defined concavity. Eadials 

 large, almost as wide as long, the lower margin but slightly convex, the 

 upper face concave in the middle and truncated at the outer sides. Cos- 

 tals very short, and not much more than half the width of the radials ; the 

 first quadrangular ; the second pentangular. Distichals 2X2, in form re- 

 sembling the radials, but only half their size. In some specimens all the 

 second distichals are axillary and support palmars, in others those of the 

 anterior ray support the arms, which vary in number from eighteen to 

 twenty. Arms stoiit, single, biserial, and arranged in groups, the tips 

 incurving and flattened ; the interspaces between the rays deeper than 

 those between their subdivisions, and in the anal interradius nearly three 



