. REPOKT ON THE GASTEROPODA. 545 



8. Bittium pigrum, Watson (PL XL. fig. 7). 



Cerithium (Bittium) pigrum, Watson, Prelim. Report, pt. 5, Journ. Linn. Soc. Lond., vol. xv. p. Ill, 



sp. 11. , 



Station 135c. October 17, 1873. Nightingale Island, Tristan da Cunha Islands. 

 Lat. 37° 25' 30" S., long. 12° 28' 30" W. 100 to 150 fathoms. 



Shell. — Tall, narrow, conical with convex outlines, blunt, flat on the base, strong, 

 opaque white. Sculpture : Longitudinals — there are on the last whorl twenty-one flatfish, 

 rounded, narrow ribs, parted by depressions of about the same form and size ; the surface 

 is also very faintly microscopically striate. Spirals — on all the whorls, except the first 

 two, there are three fine narrow spiral threads, which rise into feeble tubercles where they 

 cross the longitudinals. The first and second are a little closer together than the second 

 and third, which are separated by a flat space of about twice the breadth of the spirals. 

 Below the lowest spiral there is a rather abruptly sloping but broadish contraction into the 

 suture, close above which lies a plain, narrow, spiral thread, which on the last whorl forms 

 the edge of the base, and is there defined by an inferior minute spiral furrow. With the 

 exception of this and of very faint microscopic spirals and fines of growth, the base is 

 quite plain. Colour dead white. Spire high and narrow, with slightly convex outlines ; 

 the lowest tubercled spiral on each whorl slightly projects beyond the top of the whorl 

 which follows. Apex blunt and smooth. Whorls 13, flat on the sides, narrowed upwards, 

 constricted at the bottom above the suture. Suture minute, but well defined by the 

 furrow and by the thread which lies in the bottom of it above the suture. Mouth square. 

 Outer lip broken. Pillar short but rather narrow. Inner lip incomplete. H. 0*36 in. 

 B. 0-095. Penultimate whorl, height 0'04. Mouth, height 0*08, breadth 0*05. 



This, as regards its sculpture, also belongs to the Bittium reticulatum group. 



9. Bittium luscinicB, Watson (PI. XLI. fig. 1). 



Cerithium (Bittium) luscinice, Watson, Prelim. Report, pt. 5, Journ. Linn. Soc. Lond., voL xv. p. 112, 



sp. 12. 



Station 135c. October 17, 1873. Nightingale Island, Tristan da Cunha Islands. 

 100 to 150 fathoms. 



Shell— Small, narrow, conical, blunt, with straight outlines, rounded but not con- 

 tracted at the base, solid, translucent, glossy, white. Sculpture: Longitudinals— there 

 are 17 to 18 longitudinal rows of coarse, flat, rounded tubercles, parted by furrows narrow 

 and shallow ; these lines run very straight up the spire. Spirals — on all but the first three 

 whorls there are three equally-parted spiral threads, which rise into tubercles in crossing 

 the longitudinals ; of these three spirals the highest is the smallest and least prominent. 

 The first whorl is smooth and glossy, with a few irregular wrinkles ; the second is regularly 



(ZOOL. CHALL. EXP. — PART XLU. — 1885.) Tt 69 



