32 Cincinnati Society of Natural History. 



of the rays, from other specimens, have two rows of spines springing 

 from the marginal plates on each side of the ra^-s. 



This species has l^eeu found at different elevations from near low- 

 water mark in the Ohio river to the top of the hills at Cincinnati. 

 The specimens figured, as well as the fragments from which the fore- 

 going description was drawn, are in the collection of C. B. Dyer. 



PALiEASTER SPiNULosus, u. sp. (Plate IL, fig. 12, dorsal side; fig. 126, 

 ventral side; fig. 12a, magnified view of the madreporiform tubercle.) 



[Ety. — Spmulosus, full of spines; from the spines on the adambulacral plates ] 



Pentagonal; rays longer than the diameter of the bodj^; marginal 

 plates globular near the apices of the ra.ys, but lengthened toward the 

 junction with the body. Six of these plates measure from the body on 

 a ray three tenths of an inch. Two wedge-shaped plates form the 

 junction of the marginal plates with the body. 



Adambulacral plates a little smaller than the mai'ginal pieces, and 

 possessed of two or three spines to each plate. These spines taper to 

 a fine point, and are longer than the diameter of the plates. The 

 oral pieces are not determined. The ambulacral plates have their great- 

 est length across the raj's, and are possessed of a sharp ridge in the 

 middle which seems to be connected at one end with the adambulacral 

 pieces. 



The dorsal side is covered with plates united by angular extensions. 

 They are of unequal size, and strongly tuberculated or spinous. 



The madreporiform tubercle on its upper face is an oblate spheroid, 

 much depressed, and marked by fine radiating striae, which become 

 more numerous by intercalation, without bifurcation. 



So far as our observation has extended, the madreporiform tubercle 

 in paljeozoic asteroidea has the same form in specimens belonging to 

 the same species, but is difl'erent in diff'erent species. It will, at 

 least, be regarded, as of specific importance, in each genus. The 

 specimen figured was found at Cincinnati, and is in Mr, Dj-er's collection. 



Cyclocystoides MAGNUS, u. sp. (Plate II., fig. 8, natural size; fig. 8a, 



magnified view.) 



[^ty .—Magnus, large ] 



A flat circular body, of which only a ring, composed of twenty plates. 

 is known. Eight specimens have been examined, which differ very 

 little in size. One measured 9.10 inch in diameter, and 'the interior 

 of the ring a little more than ^ inch. 



The ring, though composed of twenty plates, may be divided into 

 two parts, an outer rim and an inner or submarginal one. The outer 

 rim is thin and bears upon the upper surface, two, three or four scars. 



