The Calceccrinidce. 403 



This first arm-joint differs from the rest, in having a wide base and 

 tapering rapidly towards its upper side, which is of the same width as 

 the succeeding two or three joints. Seven joints are preserved, and 

 110 bifurcation takes place. 



They are strongly arched, so as to be somewhat wider in their antero- 

 posterior diameter than laterally, and are higher than wide. 



Lateral arms composed of series of narrow axillary plates, five in 

 number on each side, of which the first are the highest; being as long 

 as the upper and outer sides of the lateral radials, against which they 

 rest their full length ; from these they decrease in height in regular 

 order towards the centre of the arch which they form around the first 

 two anals. Each axillary gives rise to an armlet, in which three joints 

 can be observed, when a bifurcation takes place, or a pinnule is given 

 off (exactly which, cannot well be determined on account of the im- 

 perfection of this portion of the specimen). Joints about as wide as 

 long. 



From the lower third of the shale of the Niagara Group at 

 Lockport, N. Y. 



Calceocrinus Halli n. sp. 



PI. X., Fig. 9. 

 Calceocrinus n. gen. Hall. — Pal. N. Y., Vol. II., p. 353. 



Anchylosed base triangular, broadly truncate in outline at the poste- 

 rior angle, due to the abrupt turning-in of that portion at right angles 

 with the upper surface of the piece. This bending inward extends 

 from this portion along the posterior margins laterally, decreasing 

 gradually towards the outer angles. 



Just upon the abrupt posterior curvature of the plate, is situated the 

 excavation for the reception of the articular facet for the column, 

 which is situated at the bottom of it. 



Anterior anchylosed basal very low and wide, extending laterally to 

 the outer angles of the basal piece, and having its anterior border 

 sharply grooved along its entire extent, for the reception of the elastic 

 articular ligaments. 



Lateral basals broad, due to the lowness of the anchylosed basal; 

 columnar facet situated in about the middle of the suture-line formed 

 by their union. 



Surface thickly beset with strong granules, which coalesce to form 

 larger ones on each side of the suture-lines, and upon the posterior 

 curved portion of the plate. 



Interior of plate concave, crossed by three grooves, two starting con- 

 jointly from the lateral angles and graduall}' becoming separated. The 

 posterior of these is the deepest and is formed by the projection of a 

 fold or sharp ridge along the line of curvature of the plate, and meets 

 its fellow from the opposite side in the colum-iar foramen; the othe 



