NIAGARA GROUP. 



229 



Genus HETEROCYSTITES {nov. gen.). 

 [Gr. STBpoi, varius, and xutfTig, vesica.^ 



Pelvic plates four, unequal, succeeded by ten costal plates, which alternate with cuneiform 

 intereostals 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 (n.s^.). 



PL. XLIX A. Fig. 3 a, 1), 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 intereostals 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 stria?, 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, witli the strong stride 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. 



