MOLLUSCA OP THE ' CHALLENGES ' EXPEDITION. Ill 



on the base and close to it, is another and stronger spiral. A broad, 

 shallow, but well-defined furrow lies within this, having a minute 

 spiral in the bottom of it. The pillar rises within this furrow, 

 encircled by a rather strongish spiral thread, and three moi'e finer 

 spirals twine round it. Only on the base is there the faintest 

 trace of most minute microscopic spirals. Colour pale yellowish 

 brown, quite uniform throughout. Spire high and narrow, with 

 convex contour -lines, which are strongly impressed at the suture. 

 In the upper part of the spire the whorls are a little scalar. Apex 

 broken. Whorls 9, flat, of very gradual increase. Suture im- 

 pressed. Mouth square. Outer lip broken. Pillar straight, short, 

 and broad. Inner lip formed by a thick layer of glaze, which 

 presents a narrow edge on the pillar. H. 0'14. B. 0*05. Pen- 

 ultimate whorl 0-025. Mouth, length 0-03, breadth 0-02. 



This species very much resembles C. reticulatum, Da Cos., but 

 there is appreciable difference in its contour-lines, which are 

 much more curved, and the upper whorls are scalar, while in the 

 young of that species, with the same number of whorls, the con- 

 tour-lines are straight and the outline perfectly conical. In this, 

 too, the base is more contracted and hollower than in that. The 

 apex is unfortunately broken ; but the basal part of the embryonic 

 shell is broader, less oblique, and has not the characteristic fine 

 spiral threads which encircle the base of the second and third 

 whorls in that species. 



11. Ceeithium: (Bittium) piobum, n. sp. 



St. 135. October 18, 1873. Nightingale Island, Tristao da 

 Cunha Islands. 100-150 fms. 



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 flattish, 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 



