CONTRIBUTIONS TO PALAEONTOLOGY. 127 



dose in the middle, with obsolete ridges radiating to the margins 



of the plates : radial plates elevated but not nodose in the centre, 



and with the radiating ridges well defined towards the margins. 



Interradial plates (above the first one) and interbrachial plates 



strongly nodose. 



This species has the aspect of one of the larger forms of Forbesiocrinus; 

 the height from the base to the first division of the ray being nearly one 

 inch, and thence to the second bifurcation nearly three-fourths of an inch. 



Geological formation and locality. In the shales of the Hamilton group: 

 Ontario county, N.Y. C. A. White, colle'ctor. 



RHODOCRINUS (ACANTHOCRINUS) GRACILIS (n. s.). 



EoDY small, turbinate : rays prominent; base small, pentalobate, as 

 is the upper part of the column. Easal plates small, but distinctly 

 developed beyond the column-facet : subradial plates small; first 

 radial plates comparatively large ; second and third radials a little 

 smaller; second radials two or three, below the first bifurcation 

 of the arms. One division of the ray bifurcates once, the other 

 twice; giving five arms from a single ray. Arms simple, slender, 

 composed (near the base) of a single series of plates which are 

 wider on one side, but finally composed of a double series of 

 wedgeform plates. Interradial plates small, subnodose or tubercu- 

 lose, about twelve or more visible in each series. Interbrachial or 

 interaxillary plates minute, undetermined. 



This species likewise bears a resemblance to Forbesiocrinus in the 

 prominence of the rays, and in the numerous small plates of the inter- 

 radial areas. The arms bifurcate only near the base; and in this respect, 

 it differs conspicuously from the preceding species. 



Geological formation and locality. In the shales of the Hamilton group: 

 Ontario county. C. A. White, collector. 



RHODOCRINUS SPINOSUS ( n. s.). 



Body subglobose : height and breadth about as two to three; base 

 concave; basal plates covered by the column. Subradial plates 

 large, the lower half bending abruptly into the basal depression : 

 first radial plates comparatively large, heptagonal; second and 

 third radials smaller, the third one a bifurcating plate which gives 

 origin to two simple arms. 



Interradial series consisting of seven or more plates; the first one 

 large and hexagonal, sustaining three smaller ones. Interbrachial 

 series of one or more plates. The subradial, first radial, and first 

 interradial plates large and convex, with a strong spine proceeding 



