142 PROCEEDINGS OP THE ACADEMY OP [1886. 



in this genus, is, we think, a supplementary azygous plate of no 

 fundamental importance, a plate bearing to the regular azygous 

 .plate similar relations as the small accessor}^ interradials in some 

 specimens oi Aychaeocrinus sculjjtus to the regular interradials. 



We offer the following : 



Revised Generic Diagnosis. TJnderbasals five, of vai'iable form 

 and size ; four of them quadrangular, but only three equal ; the 

 fourth one, that facing the azygous side, narrower ; the fifth pen- 

 tagonal, truncate above. Carahocrinus is closely allied to Den- 

 docriniis and Homocrinus, but differs from both in the number 

 and arrangement of its azj^gous plates. 



Basals five, four of them hexagonal ; the one toward the right 

 of the azygous plates heptagonal ; that on the left side somewhat 

 smaller, truncate below, and occupying the full width of the upper 

 side of the pentagonal underbasal. 



Radials heptagonal, the upper side excavated for the reception 

 of the brachials, which occupj' about one-third the width of the 

 plJite. The brachials, so far as known, consist of two or some- 

 times three pieces, the upper one sharply wedgeform. Arms, 

 compared with the size of the calyx, remarkablj^ short ; composed 

 of quadrangular joints with parallel sutures ; bifurcating; tapering 

 gradually to their tips. The branching is similar to that of Cya- 

 thocrinus, and the arms throughout, as in that genus, are devoid 

 of pinnules. 



Plates at the azygous side three. A supplementary azygous 

 plate rests between the basals and extends to half their height. 

 The regular azygous plate is placed between the upper lateral 

 portions of the five basals, and upon the supplementary piece ; 

 supporting with its left upper side the anal plate, with its right 

 side the right postero-lateral radial. The anal plate resembles the 

 radials in form and proportion, but its upper face is irregularly 

 convex, and is bordered by a row of small pieces which form 

 a part of the ventral tube. 



Column comparatively small, obscurely pentangular, with a 

 large, sharply pentagonal canal. The column is quinquepartite, 

 the sutures arranged alternately with those of the underbasals. 



Locality, Position, etc. Known only from the Trenton lime- 

 stone of Canada, but we found detached plates, apparentl}' of this 

 genus, in rocks of the same age near Knoxville, Tonn. 



