24 . ART. 2. — H. MATSUMOTO : 



A A — Eadial shields very rudimentary, disk entirely free of spines ; arm 

 spines all converted into compound hooks OpMosmildx. 



Oiyhiophrixus acanthinus Clark. 



OpJiiophriœus acanthinus : Claek, Bull. U. S. Nat. Mus., LXXV, 1911, 

 p. 273, fig. 137. 



Off Seno Umi, Suruga Gulf; 94-150 fathoms (Clakk). 



Key to Japanese species of Ophiohyrsa, 



A — Each dorsal arm plate represented by a zone of a mosaic of small, 

 iri'egular, secondary plates, each of which carries a spinule ; six or 

 seven arm spines not webbed together, the lowest one is converted 



into a compound hook and serves as a tentacle scale 



acantJiinohracIiia. 



AA — Each dorsal arm plate represented by a row of secondary plates, of 

 which the median two are the largest, none of them spinulate ; 



four arm spines connected together by a web-like membrane 



synaptacantJm. 



Ophiohyrsa acanthinobracJiia Clark. 



OpJiiohyrsa acanthinobracliia : Clark, Bull. U. S. Nat. Mus., LXXV, 

 1911. p. 269, fig. 134. 



Suruga Gulf; 108 fathoms (Claek). Eastern Sea; 95 fathoms 

 (Claek). 



Ojjhiohyrsa synaptacantJia Clark. 



OpJdohyrsa synaptacantlia : Clark, loc. cit., p. 270, fig. 135. 

 Eastern Sea ; 152 fathoms (Claek). 



Ophiosmilax Matsumoto, 1915. 

 Disk and arms covered by a thick skin, which may contain 



