Eight JSTew Species of Jlolocystitcs from the Nincjara Group. 131 



detevmiuation of the miiiiber. Above these, the first range consists of 

 more than twenty plates. The number cannot be exactly ascertained, 

 but four undisturbed plates, shown in the illustration, cover g-ths of an 

 inch, whore the circumference of the specimen is 3^ inches. The plates 

 are longer than wide, var}- much in width, are somewha twedge shaped, 

 and arranged alternately; two of them are hexagonal and the other two 

 are pentagonal. The second range consists of the same number as the 

 first. Nine plates, in place, extend If inches, where the circumference, 

 if preserved, would be 3^ inches or more. These plates have no uui- 

 formit}^ in shape or size; they ai-e longer than wide, and A^ary from 

 pentagonal to heptagonal. Above the second range the plates are not 

 disposed with any regularity; they differ in size from -Jth to fths of an 

 inch, and vary, in form, from a triangle to a nonagou. If the plates 

 were placed in ranges, there would be about ten between the basals and 

 the first arm base or tentacle. Two strong arm bases are shown on the 

 specimen. The apertures are unknown. The plates are perforated by 

 numerous pores, having no order in their arrangement. The specimen 

 has a length of 3 inches; diameter in the middle, If inches, and at the 

 base ^ths of an inch. 



Collected by Frederick Braun, Esq., in whose honor the specific name 

 is proposed, in the lower part of the Niagara Group, in Jefferson County, 

 Indiana. 



HoLOCYSTiTES WETHERBYi, u. sp. (Plate V. figs. 2, 2a, 26.) 



Body sub-globose, or somewhat obovate ; summit depressed convex ; 

 greatest diameter above the middle and at right angles to a line passing 

 through the mouth and ambulacral orifice. The ambulacral orifice is 

 surrounded b}' at least four arms (the specimen does not show the arm 

 bases distinctly). The mouth is on the summit, but little removed 

 from the ambulacral orifice. The other openings, whicli appear upon 

 the summit, and are shown in the illustration, served some purpose 

 not understood. The body is surrounded by four ranges of sixteen 

 plates each. The two middle ranges are composed of hexagonal plates; 

 the other two seem to be composed of both pentagonal and hexagonal 

 plates; the plates are longer than wide. The plates upon the summit 

 are not determined. There is a row of basal plates below the four 

 ranges, composed, probably, of only eight plates, but the lines are too 

 indistinct to allow them to be traced. 



Each plate of the bod}' is perforated with small holes, arranged in 

 pairs, but we have been unable to detect any order in the arrangement, 

 except so far as their arrangement in pairs is concerned. The anal 

 aperture, if it existed, is unknown. 



One of the supposed arms or tentacles is lying upon the summit of 



