l46 PROCEEDINGS OF THE ACADEMY OP [1886. 



plate at the anterior side, and therefore did not describe it. It 

 resembles Belemnocrinus in its general appearance, but differs in 

 having underbasals, and euriousl}' enough, these have a similar 

 cylindrical form, and are as solid as the basals in that interesting 

 genus. 



We have since obtained from the Burlington and Keokuk transi- 

 tion bed near Burlington, and from the lower part of the Keokuk 

 limestone proper of Tennessee, two additional specimens, clearly 

 of the same genus, but of a different species. Both specimens 

 show the same irregular structure, i. e., four arm-bearing radials, 

 and in line with them a small azygous, non-arm-bearing plate, 

 thus proving that the apparent irregularity is a persistent char- 

 acter. 



Generic Diagnosis. Form of calj^x elongate, bell-shaped, the 

 sides concave, constricted along the suture between basals and 

 underbasals. Underbasals five, large, forming an almost solid 

 ovo-cylindrical body, pierced onl}^ by a longitudinal canal. Basals 

 long and narrow, widening above, irregular in form ; three of 

 them hexagonal, two heptagonal. Radials four, of nearly equal 

 size, with an obtuse facet covering the greater part of the width 

 of the plate. Anterior radial non-arm-bearing. Like the regular 

 radials, it alternates with the basals, has the same general height, 

 but less than half their width. Brachials from two to four, ex- 

 ceptionally five ; comparatively strong ; with parallel articular 

 lines, except the upper one, which is axillary. Main arms eight, 

 which from every second joint, alternately, give off armlets, or 

 arm-like pinnules of less than half the size of the main arms, but 

 extending to the same height and branching. The arm joints, 

 from which the branches are given off, are formed almost like 

 axillary plates, one side, however, being shorter and slightly more 

 obtuse. The alternate joints are quadrangular. Whether these 

 and the axillaries are united by sj^zygy, could not be ascertained 

 from the specimens. 



Azj^gous plate large, resting between the upper sloping sides of 

 two basals, and against the right posterior radial. It supports 

 towards the left the anal plate, and at its truncate upper side the 

 first plate of the tube. Nothing is known of the ventral side. 

 Column obtusely pentangular, with a medium-sized central canal. 



