NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 279 



ent scales. Oral papillae very few and small. Teeth reduced to a 

 small cluster at apex of jaw. No tentacle scales. 



Type-species. OpJiioleptoplax megapora. 



The specimen upon which this genus rests is probably immature, 

 but I can not refer it to any known species or genus. In its mouth 

 parts it is very near OpMosyzygus, but its arm structure is quite differ- 

 ent. Yet I am not satisfied that the supposed upper arm plates are 

 really homologous with the upper arm plates of other genera. They 

 are certainly not calcareous and they may be nothing but skin 

 thickenings on each joint. Their appearance in this specimen may 

 be an individual peculiarity. 



FIG. 141. OPHIOLEPTOPLAX MEGAPORA. x 8. a, FROM ABOVE; b, FROM BELOW; c, SIDE VIEW OF TWO 



ARM JOINTS NEAR DISK. 



OPHIOLEPTOPLAX MEGAPORA, new species.o 



Disk 6 mm. in diameter; arms about 25 mm. long. Disk covered 

 with a thick, naked skin. Radial shields wanting, but upper ends 

 of genital plates are visible at base of each arm. Upper arm plates 

 represented by what appear to be very thin transparent noncalca- 

 reous scales, squarish in outline and rather wider than long; arm 

 bones plainly visible through them. Interbrachial spaces below 

 naked. Genital slits small. Oral shields very small, wider than long. 

 Adoral plates very large, much wider without than within. Oral 

 papillae, one to three on each side, minute, sharp conical spinelets. 

 Teeth (tooth papillae?) reduced to a small cluster at apex of jaw, of 

 very small, rough-pointed spinelets. Under arm plates longer than 



, signifying big, and xopoc, signifying a pore, in reference to the large tenta- 



cle pores. 



