MONOGRAPH OF JAPANESE OPHIUEOIDEA. 285 



dd — Ventral arm plates present tliroughout the entire length of the 

 arm. 



,/ — Disk covered with stout primaries and smaller secondary plates, 

 besides the radial shields ; each primary plate bearing a very large 



central umbo ; five or six peg-lik arm spines tryclinum. 



ff — Disk covered only by very stout primaries and radial shields ; no 

 central umbo on them ; three very large, acute, erect arm spines, 

 of which the uppermost and largest is x>laced on the dorsal surface 



of the lateral arm plate lütkeni. 



AA — Three pairs of tentacle pores to each radius ; genital slits provided 

 Avith papillae ; genital scales not very stout ; interbrachial ventral 

 surfaces coA'ered with many small plates or scales, without very 

 prominent central plate ; disk covered with many small plates or 

 scales, besides the radial shields. 



g — Genital slits not reaching to the disk margin ; each tentacle pore 

 provided with one scale on the abradial bjrder and often also with 

 an additional one on the adradial border ; a group of j)apill8e 

 present on either side of each arm base, just outside the genital 

 slit and radial shield ; three close-set arm spines. 



h — Oral shields triangular, about as wide as long, wider without than 



within cancellatuni. 



Idi — Oral shields pear-shaped, much longer than wide, wider within than 

 without .joUiensc. 



r;^— Genital slits reaching to the disk margin, each tentacle pore 

 provided with two scales on the abradial border ; no papillae on the 

 sides of the arm base ; oral shields triangular, about as wide as 

 long ; four well spaced arm spines laqueatiim. 



Ojyhiomusiufn scalare Lyäian. 



OpMomvsium scalare : Lyman, Bull. Mus. Comp. Zool., V, 1878, p. 117, 

 PI. I, figs. 1-3 ; Lyman, Kep. Challenger, V, 1882, p. 95, PI. I, figs. 4-6 ; 

 Kœhlee, Ann. Sei. Nat. Zool., Sér. IV, 1896, p. 308, PI. VI, figs. 24 & 



