CONTEIBUTIONS TO PALiE ONTOLOGY. 151 



the length of the body, and are still imperfect at the extremities : 

 they are composed of joints, which are longer than wide, longitu- 

 dinally striate and somewhat nodose-carinate on the back; with 

 the inner margins apparently giving origin to minute tentacula. 

 Surface of body-plates finely striate. Length of body a little more 

 than half an inch. 



The specimens which have been examined are crushed, and the true 

 form cannot be fully known; but it appears to have resembled in shape 

 the P. puzo. 



Geological formation and locality. Shales of the Hamilton group: Wes- 

 tern New- York. C. A. White and R. P. Whitfield, collectors. 



PEXTREMITES LYCORIAS ( n. s.). 



Body subfusiform, attenuate below, tapering gradually to the co- 

 lumn : base triangular; summit obtuse. The basal plates occupy 

 about one-third the entire length of the body; their upper faces 

 nearly transverse, or scarcely indented by the radial plates. The 

 radial plates long and narrow, divided for about one-half their 

 length, strongly protruding at the base of the pseudambulacral 

 fields, giving a decided pentangular form, attenuate above : inter- 

 radial plates minute. Pseudambulacral fields rapidly expanding 

 from the base upwards, and covei-ed by the pinnules so that the 

 number of poral plates cannot be determined. Pinnules extending 

 above the summit to a height equal to the length of the body, 

 which is about three-fourths of an inch. The greatest breadth of 

 the body, at the base of the pseudambulacral fields, is a little 

 more than three-tenths of an inch. 



Surface marked by extremely fine threadlike striae, which are 

 parallel to the suture - lines. Column round, long, slender, and 

 composed of very short joints. 



This species is more attenuate at base than P. pailleti, and the pseud- 

 ambulacral fields are proportionally longer. 



Geological foimation and locality. In the shales of the Hamilton group, 

 in several counties in Western New- York. 



GENUS ELEUTHEROCRINUS ( Shumard)*. 



ELEUTHEROCRINUS WHITFIELDI ( n. s.). 



Body small subelliptical, triangular and pointed at base, and trun- 

 cate at summit : length a little more than twice the greatest 

 width. Dorsal side (or side of ambulacral fields) irregularly con- 

 vex, becoming angular in the upper part. Ventral basal plate very 



* In Proceedings of Acad. Nat. Sciences, Philadelphia, 1856. 



