196 



PALJEONTOLOGY OF NEW-YORK. 



taken at any point from the commencement of the scapular plates. The subdivisions of the 

 arms from the scapular plates can be traced to the number of sixty, and many of these again 

 subdivide, and perhaps all, so that the entire number in the living and perfect animal may 

 have been one hundred and twenty. 



This is probably the same species figured by Murchison (Sil. System, pag. 672, pi. 17, fig. 

 6) as Cyathocrinus pyriformis., and is perhaps identical vpith fig. 2 of Miller's Cyatkocrinus 

 tuberculatus. The structure, however, shows conclusively that it should constitute a distinct 

 genus. The remarkable character of an undeveloped tripetaloid base assimilates it with the 

 crinoids having this structure, or three pelvic plates succeeded by five in the second series 

 (See, for example, the description and illustration of Lecanocrinus, pi. 45). 



The form of this species, with its neatly tapering base and slender column, are sufficient to 

 distinguish it from all the other species, without having particular reference to the details of 

 the structure. The arms are usually infolded at the summit, giving a well defined outline. 



Fig. 2 a. An individual of medium size, slightly compressed : a portion of the column still re- 

 mains attached. 

 Fig. 2 6. A smaller individual, having the arms extended upon the stone in which it is partially 



imbedded. 

 Fig. 2 c. A young individual of the same species. 

 Fig. 2 c+. The base of the same. 

 Fig. 2 d. The crown of another individual, where the arms are regularly incurved and enfolded, 



leaving in the centre a cavity filled with stone. 

 Fig. 2 e. A figure showing the structure as far as the third or fourth subdivisions : this structure 



is made out from an individual not otherwise figured on the plate. 

 Fig. 2/. The base enlarged, showing the three undeveloped plates, the five pelvic plates resting 



on the column, and the small space occupied by the scapular plate resting on the 



column. 

 Fig. 2 g. The same, showing the relative position of the pelvic and secondary plates. 



This structure and arrangement of plates has been observed in several specimens 



and is not the result of accident affecting a single individual. 

 Fig. 2 h, i, k; I. Successive joints from the arms and subdivisions, showing the form of the 



plate, looking upon its upper or lower surface : the margins are crenulated, and the 



projecting inner angle of the plate is longer on one side than the other. 

 Fig. 2 m. Lateral view of a fragment of one of the fingers, showing the union of the plates. 

 Fig. 2 n, 0. Fragments of columns of this species. 

 Fig. 2 p. The end of a column enlarged, showing the crenulations on the outer margin, and the 



small, circular or obscurely pentagonal canal. 



Position and locality. In the shale at Lockport. 



{Slate Collection. Collection of Col. Jewett.) 



