-ON A NEW SPECIES OF AGELACRINITES. 399 
researches have so greatly added to our knowledge of the obscurer 
organisms of the Silurian age, and who has done so much, in all res- 
pects, for the advancement of Canadian Paleontology. 
The present communication is sub-divided into two short sections. 
The first contains a detailed description of the new species. This 
description, it should be remarked, however, is founded on a single 
example. The second section comprises an analytical review of the 
genus Agelacrinites in general, more especially with regard to its 
structural relations and affinities, 
1. Description of Agelacrinites Billingsii.—Body, circular, or nearly 
so. In the specimen on which this description is based, its diameter 
exactly equals half an inch. It is slightly convex above, and flat, or 
apparently somewhat concave below. From the centre of the upper 
side, five rays, composed each of a double series of alternating or. 
interlocking plates, radiate towards the margin of the disc, and tere 
minate in well-defined points at about the twelfth of an inch from 
this margm. The rays, in the solitary specimen under examination, 
exhibit no traces of pores, even when strongly magnified. Never- 
theless, pores may have been, and probably were, originally present. 
It is easy to conceive how minute orifices of this kind might become 
obliterated during fossilization ; whilst, on the other hand, the object 
of the rays is altogether inexplicable, unless we look upon them as 
really representing ambulacral areas. Moreover, poriferous ray-plates 
have actually been discovered in certain examples of <Agelacrinites ; 
and analogy, consequently, would lead us to infer that, in all, they 
existed originally. These rays, at their origin, leave a small central 
Space covered hy larger and somewhat rhombic plates. The latter 
appear to be five in number, and to constitute the first ray-plates, one 
being common to two adjacent rays. Very possibly, however, each 
of these rhombic plates may be divided through the centre, longi- 
