126 ART. 2. — H. MATSUMOTO : 



form, acute, glassy, but not serrate, the lowest one being never 

 hook-shaped. 



This genus includes Ophiothammis ricariiis Lyman, 1869, 0. 

 qßnis Ljungman, 1871, 0. remotus Lyman, 1878, Ophioleda minima 

 Kœhlee, 1906, Ophiomitra habrotata Claek, 1911 and Ophiothamnus 

 venustus Matsumoto, 1915, the first being the genotype. 



I consider Ophioleda Kœhlee as a synonym of Ophiothamnus 

 Lyman, because I am not able to make any essential distinctions 

 of generic character between the two genotypes, judging from the 

 descriptions and figures of Lyivian and Kœhlee. 



Key to Japanese species of OpMotliamniis. 



A — Disk spines dimorphic, a few very long, acute spines being present, 

 besides very minute ones ; interbracliial ventral svufaces entirely 

 free of spines ; dorsal arm plates comparatively large, longer than 

 half the corresponding arm joint in free Imsal joints ; eight or nine 



arm spines hahrotatus. 



AA — Disk spines monomorphic, very minute ; interbrachial ventral surfaces 

 also beset Avith several spines ; dorsal arm plates very small, much 

 shorter than half the corresponding arm joint ; nine or ten arm 

 spines vennstKS. 



Oiyhiothamnûs hahfotatus (Claek). 



OpMomiira hahrotnta : Clark, Bull. Ü. S. Nat. Mus., LXXY, 1911, p. 

 182, fig. 83. 



Eastern Sea ; 95-lOG fathoms (Claek). 



OpJiiothainmis venustus Matsumoto, 1915. 



OpJiiofhamnns venustus : Matsüäk/io, Tree. Acad. Nat. Sei. Philadelphia, 

 1915, p. 63. 



Numerous specimens,; off Inatori, Izu, Sagami Sea. 



