262 ART. 2. — H. MATSUMOTO : 



1904, Ophiura megapoma Clakk, 1911, 0. penichra Claek, 1911, 

 0. liadra Claek, 1911 ; (4) species with the interbrachial ventral 

 surfaces covered with many small plates or scales, and with axe- 

 shaped ventral arm plates, viz. Ophioglyplia radiata Lyman, 1878, 

 0. ornata Lyman, 1878, 0. abcisa Lütken & Moetensen, 1899, 

 0. obtecta Lütken & Moetensen, 1899 ; besides others. 



As above indicated, the present genus is divisible rough- 

 ly into four sections, of which the first rather approaches 

 Ophiopyrgus, the second Aspidophiura, the third Stegophiura and 

 Gymnopliiura, and the fourth Opliiura s. str. 



Key to Japanese species of Ani2)Mophiura, 



A. — Interbrachial ventral surfaces entirely covered over by the very 

 large oral shield ; central rosette of the central plate, radiais and 

 interradiais very conspicuous ; dorsal, as well as ventral, arm plates 

 widely in contact with one another ; three arm spines, shorb, conical, 



acute convexa. 



AA. — Interbrachial ventral surfaces not entirely covered over by the oral 

 shields. 



a. — Each interbrachial ventral surface covered with a very large central 

 plate and very stout genital scales. 



h. — Disk covered only by the primaries and radial shields; dorsal, as 

 well as ventral, arm plates longer than wide ; a single very short 



arm spine œdiplax. 



hh — Disk covered by the primaries and radial shields and a number of 

 secondary scales ; dorsal, as well as ventral, arm plates wider than 



long ; three peg-like arm spines pompcypliora. 



aa. — Interbrachial ventral surfaces covered with many small plates or scales. 



c. — Comb papillœ S(]uarish, flat, close- set. 



d, — Oral shields not very narrow ; arm spines peg-like or spiniform, 

 not very numerous, not close-set. 



