134 Cincinnati Society of Natural History. 



six plates arranged within four arm bases. The plates surrounding 

 the orifice are narrow, pentagonal or hexagonal, and elevated so as to 

 support the arm bases. Between the arm bases on the one hand, and 

 the plates surrounding the ambulacral orifice and the first range below 

 the arm bases on the other, a small pentagonal plate fills the area; 

 these four plates with the four arm basals make eight plates in this 

 range. The mouth is situated two plates distant from the ambulacral 

 orifice, and just without a line drawn from one arm base to the next 

 adjoining. 



The body is quite veutricose, near the base on the posterior side, 

 and is slightly swollen below the mouth, on the anterior side. 



The surface is slightly granulose. All the plates are poriferous. No 

 anal aperture. 



The specimen illustrated is about one and one fourth inches in 

 length, and about an inch in diameter. The greatest diameter is found 

 in a line drawn from the left side to the right, cutting a line at right 

 angles, passing through on the right side of the mouth and left side of 

 the ambulacral orifice. 



Collected by Frederick Braun, Esq., in the lower part of the Niagara 

 Group, in Jeff'erson County, Indiana. 



HoLocYSTiTES pusTULosus. u. sp. (Plate VI., figs. 1, la.) 



{"Eiiy .—pustidosus, full of pustules.] 



Body somewhat obovate, and obscurely triangulated toward the 

 summit. It is covered by numerous, somewhat irregularly disposed 

 convex plates, which differ much in size and shape, and constitute 

 about ten ranges; the larger plates approach the summit. 



The ambulacral orifice is situated in the central part of the summit, 

 directly in the rear of the mouth, and is surrounded by five strong arm 

 bases. 



The mouth is situated in a depressed area near the margin of the 

 summit. 



A small anal aperture is situated between the mouth and the ambu- 

 lacral orifice, at the foot of an arm base, and to the right of a line 

 drawn from the center of the mouth to the center of the ambulacral 

 orifice. 



Surface marked by strongly convex plates, covered b}- many pus- 

 tules, and perforated by numerous pores. The pores open upon the 

 summit of the pustuU-s, and where the pustules are worn oft", the pores 

 may be seen in pairs, passing to tiie interior. 



Length of specinion, two and two tenths inches; circumference, five 

 and nine tenths inches; diameter from the anterior to the posterior 



