1886.] NATURAL SCIENCES OP PHILADELPHIA. Ill 



and the absence of pinnules, will be recognized by us as Hybo- 

 crinidse. 



Among the Heterocrinidae Zittel placed Heterocrinus^Oraphio- 

 crinus, Erisocrinus, Philocrinus and Stemmatocrinus. 



The family was defined as follows : Calyx regular ; base mono- 

 cyclic or dicyolic (five underbasals and five basals, or the latter 

 only); five radials ; arms long, simple, rarely bifurcating. The 

 qualification " calyx regular " cannot be applied to Heterocrinus, 

 which is one of the most asymmetrical forms of the Palaeo- 

 crinoidea, and this want of symmetry extends not only to the 

 interradial series but also to the radial plates, and forms its best 

 generic distinction. 



Neither does that term apply to Graphiocrinus, which is 

 bilateral, nor Philocrinus, which we think is decidedly irregular. 

 Only Stemmatocrinus and Erisocrinus have a pentamerous calyx, 

 but these agree in other respects with the Poteriocrinidae. 

 Heterocrinus, in its general asymmetry, in arms and pinnules, 

 and in its azygous side, closely resembles Anomalocrinus, which 

 for other reasons we refer to a distinct family. We add to the 

 Heterocrinidse the two genera Stenocrinus and Ohiocrinus, ^vhich 

 are founded upon species heretofore ranged under Heterocrinus, 

 and unlike Zittel, place Graphiocrinus, Philocrinus, Stemmato- 

 crinus and Erisocrinus under the Poteriocrinidae. 



Anomalocrinus, which we make the type of a distinct famil}^, 

 stands closer to the Heterocrinidae than to the Hybocrinidae, but 

 differs from either of them very essentially in the relative size of 

 the calyx, which is comparatively large, and low-cup or saucer- 

 shaped in place of subcylindrical or narrowly turbinate. It 

 further differs from all known Crinoids, recent or fossil, in the 

 arrangement of its pinnules, which are not given off alternately 

 from opposite sides, but from every successive joint on one side 

 at a time from one bifurcation to the next, where they change on 

 both rami to the opposite side. In the arrangement of the anal 

 plates, and in having no underbasals, the Anomalocrinidae agree 

 with the Heterocrinidae. 



The Belemuocrinidae, which only contain Belemnocrinus and 

 the imperfectly known genus Holocrinus, differ from the preced- 

 ing families in having no underbasals ; they have, however, large 

 basals, cylindrically arranged, but even these take little or no 

 part in forming the visceral cavity. In this regard Belemno- 



