THE CPaNOlU IIYPOCIIINUS. 899 



be pointed out that the genotype, Afyrtillocrinus elongatus Sand- 

 berger, is not very well known, and that Dr. Springer here b;ises 

 most of his ai-gument on M. americanus Hall, which possibly has 

 not the same structure. If, however, we accept the generic 

 identity of the two species, then it follows that Myrtillocriaus is 

 devoid of the most characteristic feature of the Gasterocomidse, 

 namely, the passage of the anus through the doisal cup. It 

 seems to me, therefore, as it did to Prof. 0. Jaekel (1895, Pal. 

 Abhandl. Bd. vii. p. 75), that the Family Gasterocomidaj is far 

 more homogeneous if Myrtillocrinus be removed from it. 

 Whether I was right in placing it with the Cupressocrinidse is 

 another matter, not worth discussion until Sandberger's type- 

 specimen has been restudied. 



Dr. Springer, on p. 138, somewhat casually mentions Hypo- 

 crinus, but leaves its systematic position uncertain. On the 

 grounds of its structure Hyfocrinus is naturally referred to this 

 Famil}^, and there does not appear to be any objection to that 

 course, except the fact that all the other genera of the Family are 

 restricted to the Middle Devonian, wheieas Hypocrinus is not 

 known below the top of the Carboniferous. This difficulty is 

 scarcely lessened if the species Lecythiocrimis adamsi "Worthen be 

 proved to belong to Hypocrmus, since that species is similarly 

 removed by a lai'ge interval of time from the rest of the Gastero- 

 comidse, being found about the horizon of Coal No. 8 of the Lower 

 Coal Measures in Peoi'ia County, Illinois. 



According to Worthen's description and figure of Lecythio- 

 crinits adamsi (1882, Bull. Illinois State Mus. Na,t. Hist. no. 1, 

 p. 37 ; and 1883, Geol. Surv. Illinois, vol. vii. p. 317), that species 

 has five infrabasals, a,nd therefore could not be referred to Hypo- 

 crinus. This fact, however, would not prevent its being placed 

 with the Gasterocomidse, since Achradocrinus also has five infra- 

 basals. The reason for placing this species with the Gastero- 

 comidse is that " Just above the summit of one of the subradials 

 [basals], and in the lateral angles of two of the radial plates, there 

 appears to have been a circular opening, rather larger than the 

 arm- facets, which is now filled with stony matter "(Worthen). This 

 no doubt is an anal opening, as suggested by Worthen himself. 



Although, for reasons of structure, Lecythiocrinus adamsi and 

 the species hitherto referred to Hypocrinus are natui'ally placed 

 in the Gasterocomidse, it should not be forgotten that this peculiar 

 disposition of the anus may have arisen independently in the late 

 Carboniferous Cyathocrinoidea. In that case, the forms in 

 question, wherever they might be referred, would not belong to 

 the Gasterocomidse. 



Hypocrinus. 



1862. Hypocrinus H. E. Beyrich, Zeitschr. deutsch. geol. 

 Gesell. Bd. xiv. p. 537. 



For other references, see " Previous History." 



Diagnosis. — A Gasterocomid with anal opening at the summit 



