PALEONTOLOGIC CONTRIBUTIONS 



41 



It thus becomes highly probable that the two types from the 

 Ithaca beds which Doctor Clarke had united under Helian- 

 t h a s t e r g y a 1 u m , are congeneric, one, L . babcocki, being 

 the genoholotype of the genus, the other, L. gyalum, a some- 

 what smaller vicarious form. As far as the abactinal side of the 



15 - 16 _ 18 



Fig. 15-18 Lepidasterella gyalum (Clarke). 15 Portion of 

 abactinal side of ray, drawn from gutta-percha squeeze, (x 5) 16 Actinal 

 view of ray (x 3) drawn from gutta-percha squeeze, shows a suture between 

 ambulacrals in middle of right side. 17, 18 Portions of the oral frame, with 

 syngnaths. (x 3) 



rays, which alone is available for comparison, is concerned, the two 

 species differ mainly in their size and the relatively stouter and 

 shorter form of the rays in the genoholotype. 



If our contention, that the smaller form, gyalum, is also a 

 Lepidasterella, is true, then we also have here the actinal side of 

 that genus, hitherto unknown ( see text fig. 16). The arrangement 

 and form of the actinal plates is very different from that of 

 Lepidaster, but identical with that of Helianthaster as figured by 

 Stiirtz ( Palaeontographica, v. 36, pi. 26, fig. 14a). It exhibits a 

 median furrow, on both sides of which rise rectangularly bent, 

 hooklike crests that delimit square areas, in the distal, outer 

 corners of which relatively small pores or depressions can be seen. 

 These crests and the pores are opposite each other, indicating that 

 the ambulacrals were also opposite. The margin of the arm is 



