16 THE VOYAGE OF H.M.S. CHALLENGER. 



and white translucency of a quill. There are two opaque bands round the apex. Sculp- 

 ture : There are traces, exceedingly faint, of fine close-set striae, which run elliptically 

 round the shell on the lines of growth, and in some lights there is just a reflection as 

 of some sort of remote longitudinal texture (very like that in Siphodentalium (Dischides) 

 hijissum, "Wood). The edge of the mouth slopes backwards very obliquely from the 

 concave to the convex side of the shell ; it is thick, and all round it is smoothly rounded 

 off. The apex projects on the convex side of the shell, and is split by four opposite, 

 shallow, unequal, irregular, rough-edged, gaping clefts, so arranged as to leave the teeth 

 at the convex and concave curves and at the two sides. The bands round the apex are 

 two narrow callus-like internal ribs. L. - 298 in. B. at mouth 0"03; at broadest 0'035 ; 

 at apex 0'017. 



This species approaches nearest to Siphodentalium (Dischides) bifissum, Wood, but that species lias 

 only two, and these lateral, narrow, deep, and regular, posterior clefts ; its mouth is squarely cut off 

 with a thin and jagged edge ; its shell is very little contracted at the mouth, and contracts slowly 

 but constantly all the way to the apex ; is also longer, more bent, and thinner. Siphodentalium 

 lofotense, Sars, and Siphodentalium 'vitrcum, Sars, which have the four posterior clefts, are totally 

 unlike in texture and in form. 



6. Sijjhudentalium prionotum, 1 .Watson (PI. II. fig. 9). 



Siphodentalium prionotum, "Watson, Prelim. Report, pt. 2, Journ. Linn. Soc. Lond., vol. xiv. p. 522. 



Station 185b. August 31, 1874. Lat. 11° 38' 15" S., long. 143° 59' 38" E. Raine 

 Island, Cape York, N.E. Australia. 155 fathoms. Coral sand. 



Shell. — Long, narrow, tapering, gently contracted at the mouth, slightly bent through- 

 out ; rather strong, polished, but hardly brilliant, translucent white. Sculpture : Very 

 faintly transversely striated on the surface, and a very minute flocculence in the same 

 direction in the texture. For the breadth of the shell the mouth is large, perfectly round, 

 oblique, with a smoothly rounded edge, which is sharp on its inner margin. The apex is 

 small, much chipped, but that in such a way as in all the specimens to produce a shallow 

 rounded hollow on either side, with a sharp projecting point before and behind. Within 

 the opening a short excessively minute riblet runs out along the middle of the posterior 

 wall ; it shines through the shell like a depression, being a little more transparent than 

 the shell-wall. L. 0-328 in. B. at mouth 0-028 ; greatest 0-039 ; at apex 0-013. 



This species differs from the previous in being much narrower and having no swelling. From 

 Siphodentalium tetraschistum, Wats., it differs in being more elongated, more attenuated behind, and 

 in the character of the posterior opening. 



1 KDtovoiroi, jagged. 



