100 CLEIOCRINUS. 



THE CALYX. 



The calyx plates are all closely abutting, — the suture lines, both between 

 successive brachials and between those of adjoining series, being marked by 

 small pits, or crenulations, indicating a union by a sort of articulation, or 

 loose suture, such as we see in specimens of Forbesiocrinus. In this respect 

 the structure is decidedly like that of the Ichthyocrinidae. There is a com- 

 plete absence of any interbrachial system, except at the anal side, where a 

 vertical series of plates, originating on the posterior basal, rises high up 

 between the arms, though not quite to the margin of the cup. The main 

 general characteristic of this calyx is the manner in which the ray divisions 

 are joined to each other by lateral union of their plates with those of their 

 fellows, and with the plates of the anal series. Billings fully appreciated 

 this when in his generic description he noted as a feature of the structure of 

 the genus its " numerously divided arms all soldered together in the walls 

 of the cup." The plates are comparatively thin, and the mode of union 

 between them imparts a marked degree of flexibility, — more, apparently, 

 than in IcMhyoennus. 



None of the specimens disclose any portion of the disk, but it is evi- 

 dent, from the manner in which they are flattened, that it was very thin 

 and pliable. Of the mouth and anal opening we know absolutely nothing. 



The arms, the manner in which the radial ridges lead to them, and the 

 structure and arrangement of the fixed pinnules, are very much like those 

 of Glyptocrinus and Rdeocrims ; but the interbrachial system of those genera 

 is entirely wanting, — there being no supplementary plates, except at the 

 anal side, whose vertical series bears some resemblance to theirs. The 

 manner of compression of the calyx would indicate a disk structure more 

 like that of Reteocrinus o' neatti and the Ichthyocrinidae. 



THE BASE. 



Examination of the specimens as they were received did not seem to 

 throw any new light upon the nature of the base. The column in specimen 

 B is obtusely pentagonal, — the exterior angles being interradial, which pro- 

 claims a dicyclic base (PI. I., Fig. 3 b). The axial canal in this specimen, at 

 about one inch from the base, is also pentagonal, and its angles coincide 

 with those of the exterior of the column (PI. I., Fig. 3/); which is a de- 

 parture from the rule of alternation, and forms another minor exception to 



