1885.] NATURAL SdENCES OF PHILADELPHIA. 31? 



ing all five rays from the base up. With the increase of inter- 

 radials and Lnteraxillaries by age, which seems to have been going 

 on continually in the specimen, more arm-plates, i. e. radials, 

 were gradually incorporated into the calyx, involving the prox- 

 imal pinnules, the plates of which arc easily recognized from 

 surrounding interradial and interaxillary pieces by being more 

 prominent. Azygous interradius wider than the four others. It 

 has an elevated ridge, composed of rather large anal pieces, which 

 are longitudinally arranged and have somewhat the appearance 

 of radials. The interaxillary areas are depressed, even deeper 

 than the interradial ones, and they consist of similar plates. The 

 ventral side has not been observed, but was evidently constructed 

 as in Xenocrinus and Meteocrinus. 

 We place here the following species : 



*1882. Canistrocrinus Pattersoni (S. A. Miller). Glyptocrinus Pattersoni, Journ. 



Cincin. Soc. Nat. Bist., vol. v July . PI. .".. figs. 2, 2 a. Ibid., vol. vi, Decbr. 



] S83, p. 226. — Reteocrinus Pattersoni, Waebs. and Sp., ISS:;, Arner. Journ. 



Sci., vol. xxv, April. 1883, p. 266. Ctica Slate, Cincinnati, 0. 

 *1880. Canistrocrinus Richardsoni [Wetherby). Type of the genus. — Glyptocrinus 



Richardsoni, Journ. Cincin. Soc, Nat. Hist., vol. ii, PI. 16, figs. I. la. W. 



& Sp., ism.— Reteocrinus Richardsoni, Rev. ii, p. 193 ; also Amer. Journ. 



Sci. vol. xxv. p. 266.— Miller, Glyptocr. Richardsoni, 1883, Journ. Cincin. 



Soc. Nat. Hist., vol. \i. p. 226. Hudson River gr., Clinton Co., 0. 



XENOCRINUS S. A. Miller. 



(PI. 6, fig. 2.) 



1881. S. A. Miller. Journ. Cincin. Soc. Nat. Hist., vol. iv. 



1881. W. and Sp. Revision ii, p. 184. 



1883. W. and Sp. Amer. Journ. Sci., vol. xxv, p. 2G6. 



Xenocrinus is closely allied to Canistrocrinus, from which it dif- 

 fers in having four in place of five basals, and a quadrangular 

 column. 



Generic Diagnosis. — Base monocyclic. Basals four, forming 

 combined a shallow decagonal cup, which upon five of its sides 

 supports the five radials. and alternately upon each of the five 

 other sides a series of small interradial pieces. This arrange- 

 ment gives to the basals, owing to their abnormal number, a very 

 irregular form, no two of them being alike. The axial canal in 

 this genus, notwithstanding it has hut four basals and a quad- 

 ranglar stem, is pentangular, its angles directed interradially. In 

 all other respects, including the ventral covering, Xenocrinus 



