PALEONTOLOGIC CONTRIBUTIONS 



61 



An interesting feature of the genotype H . f o r b e s i is that 

 the majority of the specimens in the Museum show relatively short, 

 somewhat abruptly -terminating rays, which, however, do not 

 exhibit any distinct fractures, but terminate in rounded stumps. 

 There were, however, several rays observed which attain a length 

 at least greater by one-half, and which taper to a thin, very flexible 

 whiplike portion. It is therefore probable that the rays were 

 rather fragile, without possessing, however, the faculty of 

 re j uvenation. 



Fig. 26, 27, 28 S q u a m a s t e r echinatus (Ringueberg) . 26, 27 

 Proximal and. distal portions of abactinal side of ray (x 5). 28 Portion of 

 actinal side (x 5) 



The genus Squamaster has essentially the same structure as 

 Hallaster, in its rays at least. Its adambulacrals, which also bear 

 series of spines along the distal edges, are so nearly semitubular 

 that they leave only a relatively narrow ambulacral groove on the 

 actinal side ; and on the abactinal side, at least in the distal half, 

 come almost into contact. As in Hallaster they overlap with their 

 distal ends upon the next plates and widen correspondingly in that 

 direction. Their surface where not covered by the spines is finel) ; 

 reticulate. The spines are thin and bristlelike, not thick or even 

 club-shaped as in Hallaster. The ambulacrals are opposite, the 

 podial pore or depression is in the outer distal corner, thus giving 

 the plate a boot shape, with a proximal wing or foot that surrounds 

 the pore. They lack entirely the highly projecting node along the 

 ambulacral channel, with its lateral expansions, seen in Hallaster, 

 but instead show an oblique naillike projection proximally of the 

 podial opening. On the abactinal side they meet along a sharp 

 groove with raised edges. 



The disk is in the type and only specimen folded upon itself and 

 thus not favorable for study. What appear to have been the mouth 

 frames are strongly keeled, V-shaped, elongate ossicles. 



