DescripHvn of Twelve New Fossil SjJecies. 117 



junction of the radials is very distinct, in our specimens, two thirds 

 of the distance, from the base of the pseudo-ambulacral structure, to 

 the highest extension of the plates, and the line of separation appar- 

 ently extends to the point. If there is, therefore, a plate capping each 

 of these points of extension, it is minute. This extension of the plates 

 is distinctly angular, in the middle, at the line of the junction of the 

 plates. 



No part of the ambulacral or pseudo-ambulacral structure is known. 



Prof Hall has suggested, that there is no generic distinction, be" 

 tween Codaster aud Stephanocr inus . This being the case, Stejihano- 

 crinvs has priority over Codaster, unless Conrad's geuus is to be con- 

 demned for imperfect definition and illustration. 



This species was collected in the lower part of the Niagara Group, 

 at Osgood, Indiana. The specimen illustrated is from my collection. 



PALiEASTER HARRISI, n. Sp. 



Plate X.J fig. 2, natural size. 



fig. 2a, magnified two diameters. 



Bod}- pentagonal; rays twice as long as the diameter of the central 

 part of the body, flexuous, and quite uniformly tapering, to acute 

 points, at the apices. 



The ambulacral furrows are very narrow. 



The adarabulacral plates are like small, flattened, sub-circular, in- 

 dented disks, arranged with their flattened aud iudeuted faces in con- 

 tact. The}' diminish, in size, ver\- gradually, from the body, toward 

 the points of the rays, and number from twenty-five to thirty, on each 

 side of the ambulacral furrows. 



There are ten oral plates, at the junction of the adambulacral series, 

 each one of which has a somewhat triangular outline, and extends the 

 most acute angle, toward the central part of the bod}-. 



This species is destitute of the marginal plates, which usually 

 characterize the species of this genus, aud seem to protect aud strength- 

 en the adambulacral plates, and thereby protect the extension of the 

 animal, in the ambulacral furrows. 



The ray which is broken off", at the distance of seven adambulacral 

 plates, from the oral plates, shows two plates forming the bottom of 

 the ambulacral furrow, and that the ray, at this distance from the body, 

 is covered, by five series of dorsal plates. 



The first dorsal series, upon each side of the rays, consists of sub- 

 circular plates, each of which is possessed of a sharp central spine. 

 These plates cover, upon the outside, the line of junction, between the 

 adambulacral plates aud the two series of plates, which form the bottom 



