MONOGRAPH OF JAPANESE OPHIUEOIDEA. 27 



calcified and transparent, except the outer and lateral peripheries, 

 where the calcification is complete and the plate is opaque. Two 

 or three arm spines lying flat on the arm, all coverted into com- 

 pound hooks, transparent, except the ball-like basal portions, 

 wliich are opaque. The uppermost two are subequal, about two- 

 thirds as long as the corresponding arm joint, wliile the third, 

 the lowest, is very small and about half as long as the same. 

 The smaller compound hooks have two or three denticles in one 

 plane, while the larger ones have six or seven denticles in two 

 planes, making certain acute angles with the axis of the spine. 

 Tentacle pores small, free of tentacle scales. 

 Colour in alcohol brownish yellow. 



Family 2. Trichasteridse (Dodeelein, 1911) mihi, 1915. 



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

 fine scales or granules. Eadial shields long, bar-like, forming a 

 system of radiate ribs. The radial shield and genital plate arti- 

 culate with each other by means of a transverse ridge on both 

 the plates. Genital plates long and stout, while the genital scales 

 are rather very small. Oral shields small, adorai shields very 

 stout. Teeth very stout, arranged in a single vertical row ; oral 

 and dental papillaB rudimentary as a rule, sometimes absent. 

 Peristomial plates entire, stout, soldered with the also very stout 

 oral frames. Arms exceedingly long, simple or dichotomously 

 branched, vertically coiled. Dorsal arm plates either entirely absent 

 or represented by very insignificant double rows of fine sub- 

 cutaneous scales, which are soldered together to form two, right 

 and left, secondary plates in the free arm bases of the adult in 

 certain genera ; entirely free of rows of minute hooks. Lateral 



