BATOCRINID^. 475 



Aorocrinus canaliculatus (M. and w.). 

 Plate XL V. Figs. 6a, I. 



1S69. Donjcrinus canaliculatus — Meek and "Wokthes ; Proceed. Acad. Nat. Sci. Pliila., p. 166. 



1873. Vorycrinus canaliculatus — Meek and Worthen ; Gcol. Rep. lUiuois, Vol. T., p. 381, Plate 6, 



Fig. 4. 

 1881. Dorycrinus canaliculatus — W. aud Sp. ; Revision Palseocr., Part II., p. 179 (Proceed. Acad. Nat. 



Sci. Phila., p. 353). 



Calyx below medium size, its heiglit a little less than tlie width at the 

 arm bases, the dorsal cup shorter than the ventral disk ; the former with 

 broadly truncated bottom and moderately spreading sides ; the latter de- 

 pressed conical. Plates of the dorsal cup convex, roughened by a peculiar 

 shallow pitting, which extends over the entire surface, but is more conspicu- 

 ous around the margins of the larger plates, to which it imparts a slightly 

 crenate appearance ; suture lines deeply canaliculated. The plates of the 

 ventral disk are less convex, but also defined by canaliculated sutures, and 

 roughened by a pitting like that in the dorsal cup. 



Basals extremely small ; only their outer angles visible in a side view ; 

 subhexagonal in outline, with small lateral notches at the sutures ; the col- 

 umn facet occupying two thirds the depth of the plates. Eadials once and 

 a half as wide as long, the extreme lower end bending inward to meet the 

 basals. First costals quadrangular, fully one half smaller than the radials, 

 and about once and a half as wide as long; the second quadrangular and 

 somewhat wider and longer. Distichals 2X2, as wide as the first costals 

 but still shorter. In the posterior rays both upper distichals are axillary, and 

 each one supports two palmars ; in the anterior ray only the one to the right 

 is axillary, the other bears a single arm ; the antero-lateral rays have no 

 palmars in either division, and but two arms. Arm openings arranged in 

 groups with rather wide interspaces, of which that at the anal side is almost 

 three times as wide as the others. Arms sixteen, one from each opening ; 

 rather heavy and long, incurving, their upper ends flattened and distinctly 

 serrated at the outer edges. Pinnules closely packed together ; their joints 

 but little longer than wide. First interbracbial almost as large as the ra- 

 dials ; it is followed by two plates in the second, and two in the third range, 

 the latter on a level with the arm bases, and in contact with the interambu- 

 lacral pieces. The first anal plate supports three additional anals in a longi- 

 tudinal row, which rapidly decrease in size upward, and each one of them is 



