FN TS aa, a RET ERTS kM ee RR = Oe EIS > - 
SE NTT TE IST PT aa here. 
736 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
b) 
somewhat larger, with only two arms like ‘“ Platycrinus”’ retiarws, but 
these beautifully sculptured. All these species, including Cordylocruvus com- 
tus, agree in the basals and radials with Platycrinus, but have two costals 
instead of one, and their arms are uniserial as in the young Platyerinus, their 
pinnules large and not in contact laterally. The only point of doubt, and ss 
upon which possibly a generic separation from the Gotland form might be 
justified, is that the American and Dudley specimens have whorls of cirri 
from all their nodal joints, which are not indicated in the Swedish Cordylo- 
crinus comtus. However, cirri may have been represented also in that 
species, and until their absence is satisfactorily proved, we must refer all the 
above forms to that genus. The interradial plates, which Angelin described 
as distributed in three series, in all those species form a part of the disk, 
only the lower one resting between the brachials. Hall describes a “ probos- 
cis” in “ Platycrinus” plumosus, which is imperfectly shown in the specimen, 
and it is possible that the other species have a similar structure. We propose 
the following generic diagnosis : — 
Basals and radials as in Platycrinus. Costals two, narrow, attached to a 
small facet. Arms from two to four to the ray. When four, the last bifur- 
cation takes place from the sixth, or as high as the ninth distichal. The 
arms are long and uniserial; composed either of wedge-form plates alter- 
nately arranged, or of quadrangular, transverse pieces. Pinnules stout and 
long, not in contact. The first interradial plates resting against the costals. 
Column round, with numerous internodal joints, and cirrus-bearing. The 
cirri very long, directed upward, the upper ones rising to almost half the 
height of the crown, and arranged in whorls of three to four to the arm 
| Byes joint. 
q ods Distribution. — This genus is restricted to the Wenlock group in England 
a) Oy : __ and Sweden, and to the Upper Helderberg in America. 
Type of the genus: Cordylocrinus comtus Ang). 
