360 PROCEEDINGS OP TITE ACADEMY OF [1879. 



size upward, and form so far as known a small ventral tube, which 

 has been traced to the height of the fourth or fifth arm plate, 

 where it is composed of small, very delicate, hexagonal plates. 

 The anal plates and lower portion of the tube are slightly pro- 

 tuberant, and give to the calyx a somewhat unsymmetrical aspect. 

 In species with a single anal plate in the calyx, which, so far as 

 observed, are altogether confined to the upper Coal measures, the 

 plate is comparatively small, and rests upon the posterior basal 

 and between the adjoining radials. There can be no doubt that 

 this plate is the homologue of the second anal of other species, 

 with which it closely agrees in form and position ; and that the first 

 anai plate is here absent, while the third is included in the ven- 

 tral tube. 



Column round and small. 



The upper margin of the radials is provided with a rather 

 prominent, narrow, articulating process, occupying the full width 

 of the plate, corresponding to a similar process opposite on the 

 succeeding brachial. A slit-like opening occupies the middle of 

 it to nearly one-third of its length, which penetrates the plates and 

 evidently contained the muscular apparatus. A similar structure 

 is observed between the brachial and the first arm plates. Such 

 linear processes were well adapted to facilitate the opening and 

 closing of the arms. We may further state that in all species the 

 lower portions of the brachials are pushed inward and the plates 

 incline outward, owing to the position of the hinge lines which 

 are close to the inner edge of the margin of the radial, and at the 

 outer edge of the brachial ; the outer edge of the margin of the 

 radial is bevelled. By this structure, which gives to the Crinoids 

 of this genus their peculiar subglobose form, the ponderous arms 

 obtained an important support; for when open, the tumid or spin- 

 iferous brachials rested firmly upon the protuberant radials, and 

 this explains fully the office of the brachial spines in this and 

 all similar genera. A similar articulation exists between the 

 brachials and arm plates, and also here the sutures are widely 

 gaping. 



Geological position, etc. The genus is known only from the 

 uppermost part of the Subcarboniferous and the Coal measures, 

 reaching its culmination in the latter. It is found both in Europe 

 and America, from Utali to Central Russia. 



