188fi.] NATURAL SCIENCES OF PHILADELPHIA. 119 



Family XVII. HYBOCRINIDJE Zittel. 



(Emend. W. and Sp.) 



BAEROCRINUS Volborth. 



1864. Volborth, Eine neue Crinoideen Gattung. (Author's copy, p. 85). 



1865. Volborth, Bulletin St. Petersb. Acad., vol. viii, p. 178. 



1866. Volborth, Bulletin Soc. Imp. de Nat. de Moscow, ii, p. 442. 



1867. Grevingk, Archiv. f. Naturkunde Liv.-Ehst. und Kurlands, Ser. I, 



vol. iv, p. 110. 

 18G7. Grevingk, Uber Hyhocrinus dipentas and Buerocr. Ungarni, Dorpat, 



p. 14. 

 1883. P. Herb. Carpenter, Quart. Jouru. Geol. Soc. London, Augu.-t, 



pp. 298 312. 

 1883. W. and Sp., Amer. .Jour. Sci., vol. xxvi, November, p. 365. 



Syn. Homocrinus Eicbwald (in part), 1865-66 ; Hyhocrinvt 

 Schmidt (in j.art), 1874 ; Zittel (in part), 1879. 



The genus Baerocrinus has been a subject of much controversy 

 ever since 1864, owing to doubts whether the genus should be 

 admitted or rejected. It is unnecessary to give again a full 

 history of these controversies, for which we refer to Dr. P. H. 

 Carpenter's paper " On the Relations of Hyhocrinus, Baerocrinus 

 and Hybocystites,^' and to our notes " On Hyhocrinus, Hoplo- 

 erinus and Baerocrinus,^'' in the American Journal, of 1883. 

 Carpenter agrees with us and with Volborth and Grevingk that 

 Baerocrinus is a good genus, and not, as suggested b}' Eichwald 

 and Schmidt, an abnormal specimen of Hyhocrinus dipentas. 

 There has been also much difference of opinion as to the meaning 

 of certain plates. The type specimen has on its surface, along 

 the basi-radial suture, and between two of the plates within the 

 second or so-called radial ring, a peculiar structure, composed of 

 numerous, irregular pieces, and upon this, principally, Volborth 

 founded the genus. He took this structure to be a madreporic 

 body ; while Grevingk, Eichwald and Schmidt held it to be an 

 accidental break in the test, due to mechanical agencies. Car- 

 penter considered it to be the regular anal opening. He pointed 

 out that it had the position of the anus in the Pentacrinoid larva 

 at its earlier phases. 



We stated in our paper that we did not agree with any of those 

 views. We think it possible that this structure may have served 

 as an anal opening, but as an abnormal one, which had opened 

 out when the regular opening became functionally defective. 

 We also differ from other authors in our interpretation of the 



