368 A. E. Verrill — North American Ophiuroidea. 



and cover most of the under side of the arms. They bear a row of 

 few, small, rough spines or spiniform tentacle-scales, which are 

 usually hook-like distally. Two or more rows of small plates run up 

 from each of the side plates and form transverse ridges around the 

 arms, covered with granules ; these usually bear rows of small 

 glassy hooks. The dorsal arm-plates are rudimentary or wanting. 



Teeth and tooth-pap ill se numerous, spiniform. Oral papillae, when 

 present, small, conical or papilliform. Adoral shields well-developed, 

 but usually concealed by cuticle, sometimes broken into several 

 plates. Oral shields rudimentary or wanting. Sometimes there are 

 five small madreporic plates, but usually only one. 



The three generic names : Gorgonocephalus Leach, 1815 ; Euryale 

 Lamarck, 1816 ; and Astrophyton Agassiz, 1835, were, as originally 

 used and intended, exact synonyms. As now employed, they only 

 date back to Lyman's paper on the Challenger Ophiuroidea, 1878. 



That he rightly divided these forms into thi-ee distinct genera 

 cannot be doubted, and he doubtless had the right to apply the 

 three names, as he did, to the respective groups, though it might, 

 perhaps, have saved some confusion of nomenclature if he had given 

 new names to two of the genera. 



It is certainly useless to go back to Linck, 1733, as the prior 

 authority for Astrophyton, for he was not a binomial writer. 



For the same reason it is useless to try to restore the ancient 

 pseudospecific names given by Linck and even by Seba (e. g. costo- 

 sum), when later and determinable specific names have been given 

 by binomial writers. 



Gorgonocephalus Leach (Zool. Miscell., 1815) is the oldest of the 

 three names under the binomial system. Leach gave a short diagnosis 

 of the genus, and stated that he separated it from Ophiura on 

 account of its branched arms. He mentions no special type, but 

 refers to the fact that most writers, following Linne, had referred 

 all the species to ^^ Aster ias caput-meclusmP 



As the latter was primarily based on a species of northern Europe, 

 Lyman's selection of the northern genus to bear this generic name 

 was fully justified. 



A§ for the other two names, since they were synonyms he could 

 have applied each of them to either of the remaining groups with 

 equal propriety, for each name had been used for all the known 

 species. 



There certainly is no good reason why Mr. Lyman's usage should 

 not be followed, so far as these genera are concerned. 



