BATOCEINID^. 515 



HABROCRINUS Angelin. 



Subgenus ACACOCRINUS W. and Sp. 



("Akokos simple, Kpivov a lily.) 



Calyx short, cyathiform. Basals three, equal. Radials rather large. 

 Costals two. The distichals giving off the arms, which remain simple, and 

 are composed of cuneate pieces alternately arranged, interlocking or not. 

 Interbrachials in contact with the interambnlacrals. Anal side wide, com- 

 posed of numerous plates arranged in longitudinal rows, of which there are 

 generally three. Interdistichals not observed. Structure of ventral disk 

 and form of anus not known. Column round and large. 



Distribution. — Only known from the Niagara group of Indiana. 



Type. — Acacocrinus Elrodi. 



Remarks. — We attempted at first to place the following two species 

 under Oai-pocrimis, but were unable to do so. Joh. Mliller proposed this 

 genus for " die mit den Actinocrinus bisher vereinigten Crinoideen, denen 

 audi das unregelmassige interradiale aller wahren Crinoideen felilt." His 

 definition does not ap)ply to Carpocrinus simplex, Mliller's type, if Angelin's 

 and Zittel's identifications are correct, for it has, according to their state- 

 ments, an anal plate interposed between the radials. This, it seems to us, dis- 

 qualifies Mliller's name from further use, and it will have to be replaced by 

 Hah'ocnnus Angelin. But from this, and from the subgenus Desmidocrimis, 

 our form differs, at least the typical species, in having cuneate interlocking 

 arm pieces in place of transverse single joints in Hahrocrinus, which we think 

 is sufficient to separate the two forms subgenerically, as all other species of 

 Habrocnnus have rectangular arm plates. 



Acacorinus Elrodi* W. and Sp. (nov. spec). 



Plate XXXIV. Fig. 16. 



A small species, not over 24 mm. from the top of the stem to the top of 

 the arms. The plates of the dorsal cup a little convex and smooth ; the 

 median line of the costals and distichals slightly angular. Basals forming a 

 rather large obconical cup, truncated at the end. Radials very large, as 

 long as wide or a little longer, larger than the two costals together, the 

 upper face concave. Costals wider than long ; the second smaller than the 



* Named iu honor of Dr. Moses N. Elrod, one of the pioneer geologisis of Indiana, who collected the 

 only known specimen. 



