BATOCRINID &. ATH 
Aorocrinus canaliculatus (M. and W.). 
Plate XLV. Figs. 6a, b. 
1869. Dorycrinus canaliculatus — MeEsx and Worrumn; Proceed. Acad. Nat. Sci. Phila., p- 166. 
1873. Dorycrinus canaliculatus — Mux .and Wortuen; Geol. Rep. Illinois, Vol. V., p. 381, Plate 6, 
Fig. 4. 
1881. Dorycrinus canaliculatus—W. and Sp.; Revision Paleocr., Part IL., p. 179 (Proceed. Acad. Nat. 
Sci. Phila., p. 353). 
Calyx below medium size, its height a little less than the 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 1s 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. Radials 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 2X 2, 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 interbrachial almost as large as the ra- 
dials ; 1t 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 
