40 NEW YORK STATE MUSEUM 



abactinal side with its abactinal aspect. 1 These abactinal or 

 dorsal sides of the rays exhibit now a composition of three columns 

 of plates (see text fig. 15), one of smaller median radials and 

 two columns of supramarginal plates, outside of which the narrow 

 margins of the inframarginals are seen. In Palaeosolaster the 

 abactinal side is formed by an integument bristling with spines. 

 This difference indicates already that this species can in no case be 

 a^ Palaeosolaster or even belong to the Palaeosolasteridae, but the 

 evidence of the marginal plates proves also that it is a phanero- 

 zonian. The structure and aspect of the abactinal side of the rays 

 is identical with that of Lepidasterella Schuchert, which is a 

 Helianthaster with twenty-four instead of thirteen arms. Since 

 the species under discussion has also twenty-four rays and Lepid- 

 .asterella is known only from its abactinal side, there are no facts 

 available by which this species could be separated from that genus. 

 There is, however, corroborative evidence seen in the presence of 

 an alate disk integument extending between the rays, exactly as we 

 have described it here of Lepidasterella babcocki, and 

 this integument is likewise furnished with a column of small ambital 

 marginals. It follows from this observation that L . gyalum 

 actually possessed interbrachial inframarginals, a fact doubted by 

 Schuchert who had not seen the specimens. 



The one feature which still seems to militate against a reference 

 of our species to the, Lepidasteridae is the position of the madre- 

 porite, which is very close to the mouth and actinal according to 

 Schuchert's view. The single specimen which exhibits the madre- 

 porite shows the abactinal side of the rays, and we believe therefore 

 that also the madreporite was abactinal. Furthermore the mad- 

 reporite interrupts the series of the oral ossicles, which means that 

 these must have been under it, or, in other words, on the other side 

 of the creature. The madreporite was hence on the abactinal side. 

 While in the Palaeosolasteridae the madreporite is typically on the 

 actinal side, it is in the Lepidasteridae only known of Plelianthaster, 

 where it is " marginal, large, more actinal than abactinal." Since 

 the alate interbrachial integument of the disk is quite close to the 

 oral frame (see pi. X, fig. 5) it is obvious that also the madreporite 

 of L . gyalum, on the abactinal side, was marginal in its 

 position. 



1 See, for instance, M e d u s a s t e r rh.e nanus Stiirtz, Palaeonto- 

 graphica, v. 36, pi. 31, fig. 35 ; E c h i n a s t e r i a s s p i n o s u s Stiirtz, 

 Verh. naturh. Ver. der preuss. Rheinl. v. $6, pi. 3, figs. 5 and 6, and many 

 others in Palaeontographica, v. 32. 



