ACTINOCEINID^. 589 



arm plates. Only the first palmars are in contact laterally, the othei's being 

 free. In the three anterior ra^'s only one of the distichals is axillary ; the 

 opposite one, being truncated, supports two or three more moderately large 

 cuneate distichals, which are followed by the regular arm plates. Some- 

 times, but exceptionally, both distichals are truncate, and the ray has bnt 

 two primary arms, while the other rays have three or four. The first branch- 

 ing of the arms generally takes place from the ninth to tenth double row of 

 joints, the second and third from the tenth to fifteenth above. The bifurca- 

 tions are given off at one side of the main arm, which generally has three 

 bifurcations, sometimes, however, but two ; they are widely divergent, and 

 the side-branches rarely bifurcate again. Arms heavy throughout, tapering 

 very little upward ; at each bifiarcation there is a small node, and the arms 

 themselves are slightly inflated — a peculiarity by which they are readily 

 recognized. Pinnules apparently small, their two or three proximal joints 

 provided with small hooks. Anal plate considerably narrower than the radi- 

 als. Interbrachials in two ranges ; there being one and five at the regular 

 sides, and three or two followed by five or six at the anal side. When there 

 are three plates in the first row, the middle one is narrow and wedged in 

 between the two at the sides, often barely touching the anal piece. The two 

 outer plates of the second row at each side of the area curve outward in the 

 direction of the free rays, and are largely interambulacral, touching but 

 slightly the costals ; the extended upper part resting against the covering 

 plates of the ambulacra. Ventral disk from the top of the free rays to the 

 base of the orals obconical, leaning a little to the anterior side ; broadly coni- 

 cal above ; the plates irregularly arranged, slightly convex, about equal in 

 size. The orals occupy the truncated upper face of the disk ; the posterior 

 one is located in the centre between the orals at one side and the anal tube 

 at the other ; it is strongly nodose or subspinous ; the other four orals are 

 produced into long, very heavy spines, which either gradually taper to their 

 extremities, or widen upward and fork at the top. Anal tube very short and 

 stout, directed obliquely upward ; the opening lateral, and surrounded by 

 four or five acute spines of fully one half the length of those surmounting 

 the orals. Ambulacra hidden by superimposed plates to the bases of the free 

 rays, where those of the first and second order are represented by a single, 

 strongly nodose plate. Column moderately strong, the nodal joints consid- 

 erably widest, and angular at their margins ; while the intervening ones are 

 very short. 



