This sijecimen will be distinguished by its general rough 

 form, flattened or dejiressed anterior side, veutricose upper 

 part of the left anterior side, increased size and irregular out- 

 line of plates to cover the ventricose parts of the body with- 

 out its intercalation of small plates between the ranges, by 

 the number of plates in the ranges, and by tiie four spine- 

 bearing summit jilates. If two ranges of plates are broken off 

 from the lower jjart then it is, probably, neai'er to H. ornaiissi- 

 mns, than to any other species, agreeing with it in the number 

 of ranges of plates and summit spines, but ditfering in tlie 

 shape of the body, the position of the greater tumidity, and 

 in the number of plates in each of the ranges below the sum- 

 mit. 



Pound in the lower part of the Niagara Group near Madison, 

 Indiana, and now in the collection of J. F. Hamiuell. 



HOLOCYSTITES SPIIAEKOIDALIS, n. sp. 



Plate V, Fit]. 8, summit view; Fig. 4, left side view. 



Species sessile, with a large subelliptical base of attachment, 

 that is very short. Body medium or below medium size, sub- 

 spheroidal, though bulging on different parts, most tumid in 

 the left posterior part, whei'e it is peculiarly prolonged 

 Plates small in the lower part, but medium size above, very 

 slightly convex in part and plane in \YMi, and pierced 

 with numerous jwres witliout any order of arrangement. 

 Sutures not beveled and traced with some difficulty. 



The first range of plates above the solid base of attacliment 

 is composed of very short, wide jilates that are interrupted in 

 the posterior part, so as not to make a complete circle. The 

 second range is composed of small i)lates that are longer than 

 wide on the front and sides, but wider on the posterior part, 

 and form a complete circle. The third range is similar to the 

 second, but the plates are longer. In the fourth range there 

 are twenty-seven plates, differing somewhat in size, but all of 

 them rather larger than wide. In the seventh range sixteen 

 jjlates, four of which abut upon the oral opening or mouth, as 

 shown in figure 3, and there is a small triangular plate that 

 abuts upon the mouth and cuts oiT an angle from two of 

 these plates. The eighth range surrounds the ambulaci-al 



