8 



followed by a range of eight small plates. There are eight larger 

 plates in the second range and eight still larger plates in the 

 third range without any intercalated plates. Between the third 

 range and what may be called the fourth range there are twelve 

 small plates, principally on the ventricose side. There are eight 

 large plates in the fourth range. Above the fourth range the 

 plates are polygonal of variable size and irregularly disposed. If 

 they could be thrown into ranges there would be six or seven 

 ranges between the fourth rauge and the mouth. 



The ambulacral orifice is somewhat marginal, but at the sum- 

 mit. It is subpentagonal in outline, about twice as wide as long, 

 and surrounded with seven plates. There are scars for five spines. 

 Two plates separate the ambulacral orifice from the mouth. The 

 mouth is hexagonal in outline and located subcentrally, or about 

 one-half its diameter anterior to the center, and is lower than the 

 Ambulacral orifice. A large pustule on the plate adjoining the 

 mouth and between it and the ambulacral orifice bears a large 

 pore that is called the anal opening. 



The specimen from which this species is described is almost as 

 perfect, so far as the outer test is concerned, as it was the day 

 the animal died. It is so different from all hitherto described 

 that no comparison with any of them is necessary. 



Found by J. F. Ham m ell, in the Niagara Group, near Madison, 

 Indiana, and now in his collection. 



Family ANOMALOCYSTID^. 



BELEMNOCYSTITES, n. gen. 



[Ety. belemnon, dart; Knsiis, bladder.] 



Body compressed, moderately convex in the central part on both 

 sides, but margin thin; outline ovoid. The plates are not disposed 

 in ranges or series. A marginal rim of plates that covers an 

 equal portion of both the dorsal and ventral sides is a peculiar 

 character of this genus. Within this marginal rim there are a 

 few large convex plates, on the dorsal side, without any arms or 

 apertures. Within the marginal rim, on the ventral side, the 

 plates are more numerous and an arm arises in the anterior part, 



