a ¥ oT Ta ae 
ee ee 
PLATYCRINIDA Roemer. 
Monocycttc. BRACHIALS AND INTERBRACHIALS -ONLY SLIGHTLY REPRESENTED IN THE 
DORSAL CUP; THE LOWER BRACHIALS TAKING MORE OR LESS THE FORM OF FREE 
ARM PLATES; THE LOWER INTERRADIALS IN PART INTERAMBULACRAL IN POSITION, 
RARELY ENTIRELY INTERBRACHIAL. RADIALS IN CONTACT ALL AROUND, THERE BEING 
NO SPECIAL ANAL PLATE. BASALS FORMING A PENTAGON. 
Analysis of the Genera. 
Basals 3,.unequal, frequently anchylosed. 
A. CosTALs Two. 
1. Column circular. 
a. Disk almost completely occupied by the orals ; ambulacra 
subtegminal ; orals separated from radials by only one 
ring of interradials. 
Orals symmetric; arms apparently delicate Coccocrinus. 
Orals asymmetric; arms heavy, biserial ; Culicocrinus. 
6. Disk composed of numerous plates ; orals not observed ; 
| arms uniserial, or slightly interlocking . Cordylocrinus. 
B. CosTALs ONE. 
1. Orals occupying but a small part of the disk, and asymmetri- 
cally arranged ; ambulacra exposed ; arms biserial. 
a. Column circular ; canal large, quinquelobate ; distichals 
one when more than one bifurcation ; Marsupiocrinus. 
6. Column elliptic ; canal small, round ; distichals two. 
Arms branching by alternate bainre ion Platycrinus. 
Rays extended into tubular appendages giving off 
(1K) BYOINS] = yh ees 
Eucladocrinus. 
