Oct., 1907. New Crinoids — Slocom. 291 



is said to have been collected at Joliet, Illinois, and is in the collection 

 of the Joliet High School. 



Homocrixus cylindricus Hall, Plate LXXXIV, Figures 14, 15. 



1852 H. cylindricus Hall, Pal. N. Y., Vol. II, p. 186, PI. XLI, 

 Figs. 2 and 3. 

 ' 1859 Poteriocrinus cylindricus Hall, Correct List of N. Y. Fossils. 



1879 H. cylindricus W. &. Sp., Revision Paleocrinoidea, Pt. 

 I, p. 78. Pt. Ill, p. 220. 



Calyx subcylindrical, gradually enlarging to the top of the infraba- 

 sals and slightly constricted at the arm bases. Surface of the plates 

 smooth and conforming to the general curve of the calyx, except the 

 radials which are longitudinally convex at the arm facets, giving 

 a lobed appearance to the upper part of the calyx; lobes thick. 

 Infrabasals five, equal, pentagonal, higher than wide, forming a cup 

 whose height and width are about equal. Basals four, higher 

 than wide, the largest plates of the calyx. The posterior basal is 

 heptagonal, being truncated distally for the support of the anal plate. 

 It is somewhat larger than the other four which are hexagonal and 

 equal in size. Radials five, wider than high , somewhat smaller than 

 the infrabasals. The articulating facets for the arms occupy nearly 

 the entire distal edge of the plate. The right posterior radial is smaller 

 than the others, on account of the proximal end being displaced by the 

 radianal plate. The radial symmetry is disturbed by the presence of 

 an anal plate situated between the two posterior radials and resting on 

 the posterior basal, and a radianal plate is situated at the right of the 

 anal, resting on the posterior and right lateral basal plates and carrying 

 on its distal side the right posterior radial. 



The species occurs in this locality in the form of natural casts and 

 molds. Owing to the comparative thickness of the plates the casts 

 are quite different in shape from the molds. The infrabasal cup is in 

 the form of a rapidly expanding pyramid. Owing to the convexity 

 of the inner surface of the basal plates there is a noticeable constriction 

 a little above the middle of the cast and another at the arm bases. 

 The^se features are well shown in PI. LXXXIV, Fig. 15. Hall's original 

 description* of this species is brief, and, judging from his figures, his 

 specimens were not very well preserved. There seems to be little 

 doubt, however, that this specimen should be referred to this species. 

 The species was described from the Niagaran shale at Lockport, New 

 York, and, so far as is known to the writer, has never been reported 

 from any other locality. 

 * Pal. N. Y., Vol. II, p. 186. 



