1885.] NATURAL SCIENCES OF PHILADELPHIA. 235 



The mode of union between the higher radials is either by 

 suture or articulation. A sutural union is found in the Actino- 

 crinidae, Rhodocrinidae, Platvcrinidae, Eucalyptocrinidae, and all 

 genera for which we propose the collective name Camarata. Union 

 by articulation prevails in the radials of the Ichthyocrinidae, 

 Crotaloerinidaa and the Articulata generally. In most of the 

 Ichthycrinidse, the transverse faces had muscles and ligament so 

 as to permit motion in all directions (PI. 6, figs. 3, 4). The lateral 

 faces contain deep fossaa, surrounded by a dentated margin (PI. 

 6, fig. 5). P. H. Carpenter and other writers express the opinion 

 that in Platycrinus also the first radials were united to the outer 

 plates by articulation. They evidently were led to this supposi- 

 tion by some of the figures, which show what appears to be a 

 transverse articular ridge, but which really marks out the inner 

 end or termination of the small wedge-shaped second radial. This 

 plate, in man 3' of the Platyeriniche, does not extend out to the 

 end of the scar, the remaining part being only covered by the 

 third plates. We have examined thousands of detached radials 

 of this genus, which indicate plainly that the union was in most 

 of the species by syzygy, and this explains why the upper radials 

 became so generally detached. Others are joined by a more or 

 less close suture, but none by muscles. 



The primary radials of the Camarata consist as a rule of three 

 plates, exceptionally of two or four. Platycrinus generally has 

 two, but here the second and third evidently were anchylosed. 

 Many plates show a depression indicating the former suture, which 

 in some of the earlier species is yet visible. The second radial 

 of Stereocrinus has the proportions of the combined second and 

 third of the allied Dolatocrinus, and the same is true with regard 

 to Anthemocrinus and Eucrinus. In Batocrinus the second radial 

 is short, linear, and found occasionally anchylosed with the third. 

 Four primary radials occur in Beteocrinus, and also in the im- 

 perfectly known Schizoci'inus. From Hall's figure of Schizo- 

 crinus heterodactylus, N. York Palaeont., i, PI. 28, fig. 3 a, it would 

 appear as if the first and second plate combined were equivalent 

 to the first radial in other genera, and here, as in the case of Eete- 

 rocrinus and Hoplocrinus, composed of two parts. 



In the Articulata the numbers of their primary radials is more 

 variable, and the presence of four radials by no means the excep- 

 tion ; but four are often associated in the same specimen with 



