MOLLUSCA OF THE ' CHALLENGES ' EXPEDITION. 431 



varix with a small, deep, round sinus. Sculpture. Longitudinals 

 — there are on the last whorl about thirteen rounded, rather weak, 

 slightly oblique longitudinal ribs which extend to the snout ; on 

 the fifth and sixth whorls they are fewer, but rather stronger ; 

 on the fourth whorl they are lamellar ; they are parted by shallow 

 open furrows of fully two-thirds their breadth. The whole sur- 

 face is covered with microscopic but coarse hair-like lines of 

 growth. Spirals — there are 25 to 30 close-set, flatly rounded, 

 alternatingly stronger and weaker spiral threads, of which those 

 on the shoulder and base of the last whorl are the weakest ; those 

 (twelve in number) in the middle of the body are broadest ; those 

 on the snout are the most prominent, especially the highest three ; 

 of the group on the body, the highest which comes in below the 

 sinus-area forms a very slight keel to the whorls. Colour buff. 

 Spire subscalar, high, conical. Apex consists of 1J embryonic 

 whorls, which rise regularly to a high, fine, rounded point, the 

 extreme tip of which is quite prominent. Whorls 7, of regular 

 increase, high and rather narrow, very slightly carinated, convex; 

 the last is long and narrow, nearly cylindrical in the middle ; on 

 the right side the base is scarcely contracted ; but on the left side 

 it is cut off with a long, oblique, and very considerable trunca- 

 tion, and is in this way very lop-sided. Suture not deep, but dis- 

 tinct and impressed. Mouth long and narrow, with nearly parallel 

 sides ; the short open canal is of the same width and direction as 

 the mouth itself, and ends in a rather deep nick ; the sinus above 

 is about half the width of the mouth, from which it turns off 

 through the thick lip very obliquely, and is funnel-shaped. Outer 

 lip in direction oblique and almost straight, a very little in- 

 flected, thick, its front face roundly bevelled oif to the inner 

 side, and its two sides parallel ; it is strengthened by a strong 

 external rounded varix, which extends to the front of the very 

 short snout but not to the pillar ; internally there is a slight 

 pad faintly scored by very obscure teeth, but terminating in a 

 single, small, rounded, and rather prominent tubercle on the lower 

 side of the sinus. Inner lip very narrow and thin, but with a 

 thickened pad between the sinus and the body-whorl • its direc- 

 tion is oblique, a little concave ; above it is very straight on the 

 pillar. H. 0*152. B. 0*06. Penultimate whorl, height 0028. 

 Mouth, height 0'078, breadth 0019. 



This species resembles a good deal a very small and refined 

 P. rugulosa, Phil., having the same lop-sided base ; but that spe- 



33* 



