Gd L007. NEw CrRINOIDS — SLOCOM. 287 
Order li SEL LUBALA 
Family GASTEROCOMID-%. 
ACHRADOCRINUS Schultze. 
.This genus was originally proposed by Schultze, to receive a species 
from the Devonian rocks of the Eifel, Germany. The species collected 
by the writer and here described is the first American species to be 
referred to the genus. The original description* of the genus is as fol- 
lows: “The composition of the calyx is as follows: Basalia (infrabasals) 
five, equal, pentagonal; Parabasalia (basals) five, four equal, pent- 
agonal, the fifth hexagonal; Radialia (radials) five, pentagonal, alter- 
nating with parabasalia (basals); Interradials (anal plate) one, resting 
on the horizontal, truncated edge of the hexagonal parabasal (basal) 
directly beneath the anal opening. 
Ventral dome, arms and column unknown. The base is pierced 
by a single circular canal.”’ 
Genotype Achradocrinus ventrosus. 
To the above description of the radial plates may be added the 
following, as the characters are generic: Radials five, shield-shaped; 
three regular and equal, the two posterior 
ones irregular, deeply excavated for the 
reception of the anal plate which they en- (x) 
close on three sides by meeting above. A 
prominent articular facet occupies the 
outer side of the radials near their distal 
edges. The facets are provided with a & ) (@ 
ventral groove and are pierced by a small 
canal located at some distance from the Co 
groove. 
In referring Achradocrinus to the Gas- 
terocomidae Schultze compares it with 
Gasterocoma, which it resembles in general arrangement of the plates 
and position of the anal interradius, but from which it differs in the 
form of the basal canal. In Gasterocoma the base is pierced by 
a quadrilobate canal and in Achradocrinus by a circular, central 
canal. 
So far as is known to the writer, all genera heretofore referred to 
the Gasterocomidae have been of Devonian age. 
Fig. 6, Diagram of Achradocrinus. 
(After Schultze). 
* Monographie der Echinodermen des Eifler Kalkes, p. tor. 
