344 



DISCOVERY REPORTS 



Ophiomusium constrictum, n.sp. 



St. WS871. i.iv. 32. 53° 16' S, 64° 12' W, 336-341 m. 2 specimens. 



Diameter of disk 5 mm. Arms about three times that length, apparently not very stiff. 

 Disk slightly elevated, covered with rather coarse scales, among which the primary 

 plates are not very conspicuous. Radial shields separated by a wedge of scales, some- 

 what sunken below the level of the surrounding scales. The disk scales are flat, but of a 

 rather coarse structure, as if finely granulated, this granular appearance being more 

 distinct on the radial shields. There is only a single column of fairly large scales in the 

 interradii. The ventral interradii covered with few, rather large, irregular scales. The 

 buccal shields irregular, with the proximal point separated off as a distinct little plate. 



Fig. 52. Ophiomusium constrictum, n.sp. Part of oral side («) and dorsal side (A); 

 part of arm in side view (c). . : 15. 



Mouth parts of the usual type. First ventral plate small, rectangular, with the merest 

 indication of a proximal angle. Only the two first ventral arm plates developed, and of 

 the dorsal arm plates at most that of the first arm joint is present and then quite rudi- 

 mentary. The lateral plates are strongly developed, swollen distally, constricted 

 proximally ; this constriction is limited from the swollen part by a rather distinct line 

 and forms a kind of neck, the arms being thus rather distinctly moniliform. There are 

 four rudimentary arm spines, the upper one placed a little apart from the others. 

 Tentacle pores exceedingly poorly developed, only on the first joint are they at all 

 distinct, totally lacking or merely discernible on the second joint. Genital slits very 

 short and narrow, scarcely half the length of the first lateral plate. They are surrounded 

 by some small irregular plates, the one to the adradial side being evidently the distal end 

 of the adoral plate, those to the interradial side of the slit representing the proximal end of 

 the genital scale. Colour of the dried specimens white, the radial shields slightly darker. 



