NIAGARA GROUP. 
229 
Genus HETEROCYSTITES (nov. gen.). 
[Gr. srspog, varius , and xvtfng, vesica.] 
Pelvic plates four, unequal, succeeded by ten costal plates, which alternate with cuneiform 
intercostals reaching only half way to the base of the former ; the body above this composed 
of numerous small plates, the arrangement of which has not been ascertained. 
This is perhaps a true cystidean, but the structure of the higher portions has not yet been 
ascertained. The pelvic plates present a singular inequality in their form, and the costal'plates 
are likewise equally irregular 
603. 1. HETEROCYSTITES ARMATUS («. sp.). 
Pl. XLIX A. Fig. 3 a, b, c. 
Column'?; pelvis composed of four unequal plates, one being much smaller than the other 
three; costal plates ten, nine of them of nearly equal size, and clustered about the summits 
of three of the pelvic plates ; between each two of the costal plates, except on the side nearly 
opposite the small pelvic plate, there is a cuneiform intercostal inserted, reaching about half 
way to their base ; these and the costals are succeeded by numerous small scapular and inter¬ 
scapular plates, the entire structure not being ascertained. On the side nearly opposite the 
smaller pelvic plate, there is a circular projection, like a proboscis, from between two of the 
costal plates near their summits. Each costal plate is marked near its centre by a prominent 
angular node projecting downwards ; the intercostals are similarly marked by less prominent 
nodes, as are the succeeding scapulars ; surface of plates granulated, and, near their junction 
with the adjoining ones, marked with strong striae, meeting similar ones from the opposite 
plate. 
This crinoid is a fragment having the base imperfect, so that its actual connexion with the 
column, or the base of the pelvic plates, has not been seen. The summit is likewise extremely 
imperfect, a few fragments of plates only remaining. The base, as presented in the specimen, 
has the appearance of a terminal proboscis; but the large plates connecting, as they are shown 
to do, with others, have all the characteristic features of pelvic and costal plates, and are so 
represented. The angular nodes, projecting downwards, present another character indicative 
of the relative position of these plates. At the summit of fig. 3 a, there are some remains of 
semicircular plates indicating the place of the arms. On one side there is a projecting process, 
the structure of which can not be determined ; but it appears to be connected with the body, 
and was probably the mouth or ovarian aperture. 
Fig. 3 a. Profile view of the specimen, showing the form of plates, the angular nodes, and the 
projection on one side indicating an aperture, marked o. 
Fig. 3 b. Several plates enlarged, showing the granular surface, with the strong strife at the 
junction of the plates. 
Fig. 3 c. The structure as far as can be ascertained from the specimen, showing position of 
aperture at o. 
