394 The CalceocrinidcB, 



such a manner as to allow of a partial but not complete erection of 

 the calyx upon the base. 



Trenton formation, Belleville, Ont. Type in the collection of 

 W. K. Billings. 



€a§tocrinu§ t>illing^§ianus n. sp. 



PI. X., Fig. 3. 



Calyx broad, wider than high, base broad, central portion of calyx 

 depressed anteriorly and laterally, just above its middle. Posterior side 

 evenly rounded, with a median furrow for the reception of the column, 

 against which it rests. Anterior arm simple (?), lateral and posterior 

 arms bifurcating. Ventral tube tapering. Column of medium size. 



Base of anterior side of calyx with three semicircular depressions, of 

 which the median is the largest, and has the sharpest curvature ; late- 

 ral depressions well curved on their inner sides, but gradually rounding 

 out towards the lateral angles. The consolidated basal has a shallow, 

 well-defined, median depression, corresponding to the one on the oppo- 

 site side of the hinge-line. Lateral depressions but faintly defined. 

 Two ligamentous bands pass over the hinge-line from the dentate pro- 

 jections left on either side of the opposite median depressions. 



Consolidated basal piece broad, evenly rounded from side to side, 

 about twice as wide laterally as antero-posteriorly. It is composed of 

 three plates, the anterior basals being anchylosed. Columnar facet 

 situated on the posterior side of the curved portion, from the side of 

 which the column projects in the same general plane as the piece. 



Anterior anchylosed basal evenly tapering by slightly sinuous lines to 

 the point of juncture with the column. Its base occupies something 

 over half of the anterior margin of the plate, and has two dentate pro- 

 jections near the lateral angles, receiving the median depression between 

 them. 



Lateral basals about as wide at their distal as at their proximal ends. 



Anterior radial high, moderately narrow, with a contraction at its 

 upper third ; basal end wider than the brachial end. Lateral radials 

 pentagonal, with the lateral angles truncated. 



Posterior radials small, triangular, the right (arm-bearing) radial 

 being somewhat larger than the left. 



Azygous unknown. The right posterior brachial is somewhat higher 

 and larger than the left, and has its upper angles projecting upward, 

 and clasping the base of the succeeding brachial between them, differ- 

 ing in this respect from the left pentagonal brachial, which supports 

 the large anal plate. But three anal plates have been observed; they 

 are large, quadrangular, and rapidly tapering towards the apex of the 

 tube. 



Anterior arm simple as far as observed, tapering for the first two 



