366 PROCEEDINGS OP THE ACADEMY OF [1888. 



sichtbar.' According to our interpretation, the calyx of the Crotalo- 

 criuidae extends ventrally to the oral pole, and the ambulacra, 

 central piece, and proximals are subtegminal, covered by interradial 

 plates, which extend out to the lower rows of covering plates and 

 side pieces (Icon. Criu. Suec, PI. VIII, fig. 6, and PL XXV, fig. 2). 

 A similar condition probably prevailed in the Ichthyocrinidae, with 

 which the Crotalocrinidae have close affinities." 



As our reference of these genera to the Articulata was based ex- 

 clusively upon the figures, especially those of Angelin, it will be well 

 to examine them now in the light of the knowledge we have since 

 obtained. The only figure of those quoted that gives the vault 

 structure correctly, is fig. 3a, on Plate XVII. It shows very plainly 

 four large proximals and a large plate toward the posterior side, 

 which, according to the terminology we then employed, we regarded 

 as a central plate. The proximals are elongate-nail-shaped, and 

 two of them touch the incurved ends of the upper faces of the first 

 radials, while two others abut against a small interradial plate, and 

 the larger posterior plate against small plates around the anus. 

 Within the re-entering angles, between every two of the large plates, 

 there are several series of small j^ieces ramifying toward the arm 

 oj^enings and laterally connected. Dr. Lindstrom has sent us a 

 very carefully prepared drawing of a specimen which he thinks is 

 the original of the above mentioned figure. This is rei)roduced by 

 us on PL XX, fig. 4. The structure appears substantially the same, 

 but the details are better defined in this figure than in the former, 

 showing that the proximals touch the fii'st radial only at one side, 

 while at the other sides one, two, or three small interradial plates 

 are interposed. Within the five re-entering angles formed by the 

 five orals (central plate and four large proximals),* rest five com- 

 paratively large radial-dome-plates, Avhich are followed by several 

 rows of small alternating pieces. That the latter are covering 

 plates which were continued along the arms is well shown in both 

 figures. 



A totally different structure was exhibited by figs. 6 and 7, PL 

 VIII, of Crotalocrinns pulcher, and by fig. 3a, PL VII, and fig. 2 

 PL XXV, of Enallocrinus scriptus, all purporting to show the plates 

 of the ventral side completely. In all of these figures the arrange- 



*The so-called '• proximals" and "central plate," as we have shown else- 

 where, are now regarded by us as representing the five oral plates, the central 

 plate being the posterior oral, modified and displaced by anal struclures. 



