120 NEW YORK STATE MUSEUM 



given by the six species classed by Schuchert under Hudsonaster^ or 

 perhaps more properly from the three good specimens which he 

 refers to P . n a r r a w a y i , for he suggests ( 1915, page 59) that 

 these speciraens are perhaps generically distinct from the othe;r 

 species of Hudsonaster and that Protopalaeaster (accepted by 

 Spencer in 1914) may have to be revived. My studies of the holo- 

 type (1912, 1913a, 1913&) will show that the four good specimens 

 now referred to this species should receive more detailed analysis. 



No attempt will be made to redefine my proposed ncAv order of 

 sea stars, for Spencer's careful work certainly should make this 

 field his own, but I shall enter here a protest against the use of the 

 terriis ambulacra and adambulacra in any class of echinoderms 

 save the Echinoidea. Whether the plates there designated by these 

 terms are homologous with the plates so named in Crinoidea or 

 Asteroidea we do not know, but we do know that in the last two 

 cases they are applied to plates having entirely different origins. 

 The terms are intrinsically meaningless so far as their application 

 to echinoderms is concerned and they are both cumbersome and 

 confusing. Their use will therefore be abandoned here and the 

 terms floor plate and cover plate, as used by Bather in his " Studies 

 in Edrioasteroidea," accepted in their place. 



Urasterella clearly shows that the food groove is an organ apart 

 by itself, with a cover plate for every floor plate, and this organ 

 shows also an utter disregard for the serial arrangement of the 

 inframarginals. The presence of a food groove similarly con- 

 structed is as apparent in Blastoidocrinus as it is in Edrioaster and 

 is also found in Blastoidea, Crinoidea and Cystidea. So primitive 

 and fundam.ental a structure and one so essential to alimentation in 

 most echinoderms should have a truly descriptive terminology, and 

 one so applied to all forms retaining the food groove as to assist in 

 keeping the homology in view. 



Raymond (December 1912, plate VI) figured a specimen of 

 Urasterella from the Museum of Comparative Zoology, Cambridge, 

 Mass., to show that a fossil sea star might be so weathered as to 

 lose most of its apical skeleton and reveal the apical surfaces of its 

 floor plates. Doctor Raymond, afterward, very kindly loaned me 

 this specimen for study. It shows much that is new to our present 



1 The six species of Hudsonaster will probably be reduced to five, 

 for according to Bather (191S, 'p. 425-26) he and Spencer are agreed that 

 in H. batheri, Schuchert mistook an apical aspect of Tetraster 

 wiville-tbompsoni for an oral aspect of a new species. 



