132 PROCEEDINGS QP THfi ACADEMY OP [1886. 



described under HeterocrinuSj and noted under that genus in 



Rev. I, p. 70 : 



*Stenocrinus heterodactylus, the U'pe of the genus, and its variety prophi- 

 qnut ; *S. exilis Hall (not Meek): 'S. juvenis; S, Milleri, and perhaps 

 Heterocrinus tenuis Billings. 



To these we add : 



*1883. Stenocr. bellvillensis (W. R. Billings), Heterocr. bellvillensis, Ottawa 

 Field Naturalist's Club. Trans. No. 4, p. 49 with plate. Trenton liniest. 

 Bellville, Ont. 



*(?)1879. S. genioulatus (Ulrich), Heterocr. geniculatus, Journ. Cincin. Soc. Nat. 

 Hist. (April), PI. 7, fig. V^. Utiea Shale. Cincinnati, Ohio. This species 

 differs too much from the other species to be left under Stenocrinus, but the 

 only specimen which we examined was not sufficiently perfect to warrant a 

 satisfactory generic description. 



*1882. S. pentagonus (Ulrich), Heterocr. pentagonus, Journ. Cincin. Soc. Nat. 

 Hist., p. 176, Pi. 5, figs. 10, 10((. Hudson River gr. Cincinnati, Ohio. 



OHIOCRINUS, nov. gen. 

 (Heterocrimis Hall, in part.) 



This form is closely allied to Stenocrinus^ but differs from that 

 in two points : the form of its arm appendages, and in the con- 

 struction of its ventral sac. 



The plates of the calyx are arranged as in Stenocrinus, and 

 also the column is strong, pentangular and pentapartite. The 

 arms, which are ten, do not bifurcate, and are provided with stout 

 pinnules, given off alternately from every fourth or fifth plate. The 

 pinnules are long, bifurcating, and extend to the tips of the arms. 



The ventral tube rests upon the left sloping side of the right 

 posterior radial; it ascends spirally, and in such a manner that 

 adjoining convolutions touch each other, being perhaps suturally 

 connected. It is composed of numerous hexagonal pieces, 

 arranged alternately, and in longitudinal rows. 



Column strong ; indistinctly pentangular ; pentapartite. The 

 older stem joints are rather long pieces which have a well-marked 

 pentapetaloid concavity upon their articular faces. The j^ounger 

 joints consist of five small convex leaflets, disconnected laterally, 

 which fill the concavity of the older joints, exposing to view along 

 the lateral face of the column a small trigonal piece. A similar, 

 if not the same, columnar structure is found in Stenocrinus.^ 



' Ohiocrinus resembles Stenocrinus very closely, and can only be upheld 

 by the form of the ventral tube. We never saw the appendage of Steno- 

 crinus, but Mr. S. A. Miller claims it to be distinct, and this induced us to 

 make the separation. 



