Oct., 1907, New Crinoids — Slocom. 289 



vertically and is not visible in a side view of the calyx. In A. 

 patulus, however, the opening is in line with the center of the arm 

 facets, directed horizontally and visible only in a side view of the 

 calyx. 



Locality: The type specimen, Mus. No. P 8417, is a silicified dorsal 

 cup in a good state of preservation. It was collected by the writer 

 in the clay pockets of the Niagaran limestone at Romeo, in the fall of 

 1905- 



Family CYATHOCRINID/E. 



HOMOCRINUS Hall. 



No members of this genus have been heretofore reported from this 

 area, but two species, H. ancilla and H. cylindricus, were collected by 

 the writer and are here described. The generic description is as fol- 

 lows: Calyx dicyclic, subcylin- 

 drical to turbinate. Infraba- 

 sals five; basals five; radials 

 five, separated on the posterior 

 side by an anal plate. The 

 radianal plate is situated below 

 the right posterior radial and 



between the right anterior Fig. 7- Diagram of Homocrinus. (After Bather). 



radial and the anal plate ; ven- 

 tral sac long and large ; arms bifurcating, without pinnules ; stem round. 

 Distinguished from Dendrocrinus by the proportionally larger infraba- 

 sals and from Poteriocrinus by the arrangement of the azygous 

 plates. 



Homocrinus ancilla Hall, Plate LXXXV, Figures 9-1 1. 



1879 Dendrocrinus ancilla Hall, Trans. Alb. Inst., Vol. X, p. 9. 



1882 Dendrocrinus ancilla Hall, nth Geol. Rept. Ind., p. 271. 



1886 Homocrinus ancilla W. & Sp., Revis. Paleocrinoidea, Pt. Ill, 

 p. 220. 



Hall's description of this species is as follows: "Body narrowly 

 turbinate, width and height above as ten to twelve or ten to thirteen; 

 contracted between the arm bases ; upper part of the column closely 

 adhering to the body, the five minute basal plates (infrabasals) scarcely 

 distinguishable from the segments of the column at its summit; sub- 

 radial plates (basals) obscurely angular on the lower face, about 

 three-fourths as wide as long, very gradually expanding in width from 

 the base, and supporting on their upper adjacent sloping faces a large 



