326 . REPORT ON THE STATE CABINET. 



The ventral surface shows a range of marginal and one of adambulacral 

 plates, the latter much smaller, but the same in number and alternating 

 with them. Two ranges of poral plates are visible in the groove, each 

 one being more deeply excavated on the inner or posterior, than on the 

 outer margin, to form the pore. 



These features of the ventral side have been ascertained by removing 

 a portion of one of the rays from the original specimen. 



Oeological Formation and Locality. — The specimen figured is from the 

 Trenton limestone at Trenton Falls, and I have seen another specimen 

 from the same neighborhood. 



Pal^aster sh^fferi, n. s. 



PLATE IX, FIG. 1. 



Body of about medium size, composed of five tapering, acutely pointed 

 rays, which, in the specimen examined, measure seven-eighths of an 

 inch from the centre of the disc to the extremity. The lower side 

 of the ray is formed of two ranges of plates bordering the ambula- 

 cral groove. The marginal range consists of moderately convex 

 plates which gradually decrease in size from the base to the extremity 

 of the ray, twenty-two or twenty-three in number, besides a small 

 terminal one at the angle of the range ; each plate of the marginal 

 range is marked on its outer surface by a comparatively large cicatrix 

 for the attachment of a strong spine. The inner range of plates 

 (adambulacral) are somewhat smaller, about the same in number, 

 alternating with those of the marginal range ; the basal pair (oral 

 plates) are elongate-triangular, and slightly constricted near the 

 middle. Ambulacral areas narrow, composed of a double range of 

 poral plates, which at the middle of the ray are about of equal 

 length and breadth. Pores not observed. Upper surface of the ray 

 composed of three ranges of subnodose plates, the outer ranges 

 bearing a strong spine on each plate : the central range apparently 

 destitute of spines. 



This species difiers from P. (^Asterius) antiqiia, Troost, in the more 

 slender and acutely pointed rays, and in the smaller marginal plates, the 

 basal one of which is quite different in form, that one being triangular 

 with the apex towards the axil of the ray. The ambulacral range also 

 differs in number of plates ; Troost's species having about twice as many 

 in the marginal range. 



