NIAGAKA GKOirP. 



203 



593. 4. LECANOCRINUS CALICULUS {n. sp.). 



PL. XL VI. Fig. 3 a, b. 



Calyx cup-form, base concave for the insertion of the column ; pelvic plates comparatively 

 large, not closely anchylosed ; costal plates as in the first two species, two of them heptagonal 

 from the insertion of the intercostal plate ; scapular plates broad and spreading, with a hexa- 

 gonal interscapular plate. Arms unknown ; column round. 



This species is sufficiently distinguishable from any of the preceding. The cup is more 

 spreading than in either species described, and the pelvic plates proportionally larger. The 

 small intercostal plate is quadrangular, as in the two first described ; but the costal plates, on 

 either side of the intercostal plate, are more regular and angular in form than in the first 

 described species, and differ in other respects from the second. The surface of the specimen 

 figured is too much worn to preserve any traces of marking. On the base of the pelvis, the 

 impression of the stem shows that the joints were crenulated towards the margin, but not near 

 the centre. The canal is pentangular, three of the angles corresponding to the divisions of the 

 three plates, and one in the inner margin of each of the broader plates of the pelvis. 



Fig. 3 a. The fragment described, showing intercostal and interscapular plates. 

 Fig. 3 b. Shows the structure of the specimen and arrangement of plates. 



Position and locality. In the shale at Lockport. 



Genus M ACROST YLOCRINUS. {nov. gen.). 

 [Gr. (AKxpos', longus, drxiXoi, stylus, and xpivov, lilium.] 



Pelvic plates three, costals five, large ; scapular plate, resting on the truncated upper edge 

 of the costal, and supporting an arm-plate from which proceed a pair of arms ; a single inter- 

 scapular plate between two or more of the arms, succeeded by two interbrachial plates. 



This genus is more simple in the structure of the cup than Lecanocrinus ; the costal plates 

 supporting, in direct line, the scapular and arm-plates, making but a single alternation in the 

 principal plates of the calyx. Since a single species only has been seen, it is impossible to know 

 positively whether the characters of interscapular and interbrachial plates, as well as the struc- 

 ture of the arms, are of generic importance. 



In its inception, the structure of this crinoid is similar to that of Platycrinus ; but there is a 

 prominent scapular plate interposed above the broad costal plates, which does not exist in that 

 genus, where the arm-plates rest on the summit of the plates of the second series, which are 

 regarded as the scapular plates, and correspond in position to the costals of this one. In the 

 intermediate plates between the arms this crinoid is likewise similar to Platycrinus, as also 

 are the succession and subdivision of the plates of the hands and fingers, to some species of that 

 genus. 



