GENUS HOLOCYSTITES. 313 



Formation and locality. In limestone of the age of the Niagara group 

 at Racine, Wisconsin. 



HOLOCYSTITES WINCHELLI ( n. s.). 



Body clavate or elongate ovate, ventricose above and the summit abruptly 

 rounded ; rapidly contracting towards the base, which is unknown. The 

 subcentral aperture of the summit is very large. The form is unsymme- 

 trical, being flattened on one side and arcuate, perhaps partially from 

 accident. 



The specimen described is imperfect at the base, but from the aperture 

 at the summit to the broken lower extremity it preserves eight ranges of 

 plates. The lower ones are hexagonal and in alternating series ; but ap- 

 proaching the summit and following the curve of the arcuation, there are 

 apparently three or four plates in direct succession, which are truncate 

 above and below, but maintain a hexagonal form from becoming wider 

 above, and having a short sloping side adjacent to the upper straight margin. 

 This species is readily distinguished from the three preceding ones by 

 the elongate-ovate ventricose form, and the more numerous ranges and 

 smaller plates, as well as their arrangement in direct succession. The two 

 or three lower ranges of plates preserved, somewhat resemble those of H. 

 cylindricuSj but they are quite free from nodes. It is impossible to know 

 the entire number of ranges of plates from the base upwards, since there 

 are no perfect specimens in the collection. In the circumference there are 

 fourteen or sixteen plates, there being some obscurity on one side. 



The specimen preserving eight ranges of plates has a length of about 

 two inches, and the diameter where broken off below is more than half an 

 inch. A section below the summit is subelliptical, having its greatest dia- 

 meter nearly an inch and a half, and the shorter diameter a little more 

 than one inch. 



Formation and locality. In the limestone ( Niagara group) at Wauke- 

 sha, Wisconsin. 



The two following species, both on account of their form and the great 

 number of small polygonal plates, may prove distinct from the typical forms 

 of this genus. 



HOLOCYSTITES OVATUS ( n. s.). 



Body from the summit to near the base symmetrically ovoid : a little de- 

 pressed at the central aperture, and elevated at the excentric one ; sides 

 regularly curving : composed of more than ten ranges of alternating 

 polygonal plates, which are as wide or wider than long, elevated in the 

 centre, and coarsely granulose. 

 [December, 1864.] 40 « 



