PALEOZOIC FOSSILS. 291 



Rays, as seen from the ventral side, narrow, attenuate, with the ambula- 

 cral plates curving, and, near the base of the rays, a little wider than 

 long, and towards the extremities longer than wide, with a strong eleva- 

 ted transverse ridge. There are about eight pairs of plates enclosed 

 within the limits of the disc. Pores penetrating the interstices near the 

 outer extremities of the plates, while near the inner end there is a depres- 

 sion or pit resembling a partially excavated pore. The adambulacral plates, 

 as seen from below, are extremely narrow and very convex on their outer 

 surfaces forming the margins of the ray. Oral plates in pairs, narrow and 

 elongate. 



This specimen measures, from the centre of the disc to the extremities 

 of the rays, about one inch and a half : the widest part of the ray, which 

 is near the margin of the disc, is about an eighth of an inch in diameter. 

 The rays, toward their extremities, have the ambulacral field covered by 

 the curving of the marginal plates over the groove ; and which, closely 

 uniting by their margins, give a teretiform termination of nearly one-third 

 the entire length ; each one having the aspect of a slender crinoidean 

 proboscis. 



Geological formation and locality. In the Hamilton group, near Fenner 

 in Madison county, New-York. The specimen was collected during the 

 geological survey, and is now in the State Museum. 



GENUS PTILONASTER (n.g.). 



[ Gr. "ktlIov, penna ; aarep, aster.'] 



Form and general features as in Eugaster, but differing in the plates of 



the rays. 

 Rays composed of an ambulacral, adambulacral and marginal series, which 



are united by their edges, and apparently not imbricating, the projecting 



or oblique anterior face of the marginal plates bearing spines which are 



inclined towards the extremity of the ray. Margins of the rays alated by 



the extension of the disc. 



I had originally united this form with Eugaster ; but farther examina- 

 tion has shown the ray to have a range of marginal plates outside of tho 

 adambulacral plates ; and I am unable to discover any such feature in 

 Eugaster logani. 



This and the preceding genus belong to the Ophiurid^, to which may 

 also be referred the Genus Protaster. 



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