251 



spine-like hairs all over the surface. All the segments of these cirri bear two pairs of ver)' 

 long spines on their inner face (PI. XXVI, fig. 14). Between the spines of the lower pair a 

 few very short hairs are disposed, and between those of the distal pair of spines a few 

 somewhat longer hairs. The hairs on the dorsal surface near the extremity of each segment 

 are relatively short. 



Penis (PI. XXVI, fig. 15) in all the three specimens examined extremely short, its 

 free extremity not extending to the end of the pedicel of the sixth cirrus (PI. XXVI, fig. 16). 

 It is broad at the basis and much narrower at the extremity ; this narrower part seems to be 

 somewhat longer in the specimens from Stations 59 and 105 than in that from Station 251. 

 The penis is finely-ringed and bears only a few hairs. A tuft of hairs is seen round the tip. No 

 projecting point was observed at its dorsal basis. 



The specimens of this interesting species were collected at the following stations : 



Stat. 59. April 26, 1899. Lat. io°22'.7S., Long. i23°i6'.5E. Western entrance Samau-strait. 

 Depth 390 m. Bottom : coarse coral-sand with small stones. One specimen, which 

 was separated from its bottom. 



Stat. 105. July 4, 1899. Lat. 6° 8' N., Long. 121 19' E. Depth 275 m. Bottom: coral (a very 

 short haul, dredge almost immediately caught in the bottom). Two beautiful white 

 specimens attached to the surface of a piece of shell. 



Stat. 251. December 8, 1899. Lat. 5°28'.4S-, Long. i32°o'.2E. Depth 204 m. Bottom: hard 

 coral-sand. Trawl brought up pieces of grey clay and manganese nodules, the 

 interior of which consisted of dry clay. Two specimens, one of which was broken 

 and loose, the other being attached to a piece of brown stone. 



General Remarks. As I have pointed out already, the resemblance of the different 

 specimens of this species collected by H. M. S. "Siboga" is not complete. There can be no 

 doubt, however, that they belong together and that they represent a species different from 

 those already described by Pilsbry and myself. 



2. Hexelasma arafurae n. sp. PI. XXV, fig. 12 — 16. 



Alae broadly-triangular with their summits oblique. Shell with very wide orifice, dirty 

 white, without epidermis, with obscure longitudinal stripes. Inner side of scutum and tergum 

 orange-coloured. Scutum indistinctly folded longitudinally, with the articular ridge slightly pro- 

 minent and a deep pit for the adductor muscle ; tergum beaked, with prominent articular ridge 

 and the extremity of the spur broadly rounded. 



Shell (PI. XXV, fig. 12) dirty white, compartments rather thick, massive, standing nearly 

 vertical, hence orifice very large, diamond-shaped, somewhat narrower towards the carinal 

 end. Outer surface of shell with horizontal and not very distinct lines of growth, slightly more 

 distinct on the surface of the rostrum. No radii present. Alae of the carina, the carino-lateral 

 and lateral compartments broad, triangular, with strongly marked lines of growth and the upper 

 margin irregular, partly broken off, giving the orifice a toothed appearance. The rostrum when 

 seen from the inner side has the sheath developed only in the middle part — whether the 

 lateral parts represent rostral-lateral compartments cannot be made out. Parietes not porose, 

 nor furnished with ribs at the inner side. Basis not distinct, membranous. 



