254 ART. 2. — H. MATSUMOTO : 



than wide at the base, tapering outwards very rapidly, with very 

 acute extremity. Dorsal arm plates very well developed, widely 

 in contact with one another. Lateral arm plates high. Ventral 

 arm plates quadrangular, widely in contact with one another. 

 Numerous arm spines, short, spiniform or peg-like, often dimorphic 

 and arranged in two rows. Tentacle pores very large, with very 

 numerous scales. 



This genus includes Ophiura nodosa Lütken, 1854, 0. stuioitdi 

 LüTKEN, 1857, Ophioglpyha elevata Lyman, 1878, 0. sculpta Duncan, 

 1879, 0. sladenl Duncan, 1879 {=Ophiura stiphra Claek, 1911) 

 0. striata Duncan, 1879, 0. sterea Ci-akk, 1908, Ophiura hrachyac- 

 tis Clark, 1911, &c., besides Stegophiura vwipara Matsumoto, 1915, 

 the first species being the genotype. 



Key to Japanese species of Stegoxjhiura, 



A. — Arm spines subequal, arranged in a single series. 



a. — Oral shields very large, almost entirely covering the inter- 



brachial ventral surfaces, quite reaching to the disk margin ; arm 



spines minute, flat, fitting into small notches on the inner margin 



of the succeeding lateral arm plate striata, 



aa. — Oral shields not very large, not reaching to the disk margin ; arm 

 spines spiniform, acute, free of notches. 



b. — Radial shields of the same radius overlapping each other ; oral 

 shields pear-shaped ; seven or eight arm spines, including the tentacle 

 scales, which are indistinguishable from the spines vivipara. 



hh. — Radial shields not overlapping, but joined in pairs ; oral shields 



pentagonal ; eight arm spines sculpta. 



A A. — Arm spines dimorphic, arranged in two rows. 



c. — Arm spines well spaced, not soldered together. 



d. — Comb papillae not very numerous, short, flat, blunt ; three to six 



