MOLLTJSCA OF THE ' CHALLENGER ' EXPEDITION. 117 



17. Cebithium (Bittium) oosimense, n. sp. 



May 14, 1875. Oosima, Japan. 



Shell. — Small, broadish, conical, pointed, whorls angulated, 

 semi-imbricated, corrugated longitudinally, not reticulated, tuber- 

 cled, variced, thin, brownish grey, with white and brown spots. 

 Sculpture. Longitudinals — there are on the penultimate whorl 

 13 depressed, rounded, slightly oblique ribs or corrugations, 

 parted by furrows, shallow, rounded, and narrower than the ribs. 

 These ribs diminish in number upwards on the spire, down which 

 they run from whorl to whorl, with a slight oblique twist from 

 left to right. On the last whorl one of these is strengthend into 

 a feeble varix, but the rest become increasingly inconspicuous, and 

 at last scarcely recognizable ; on the base they are still traceable 

 as faint corrugations. Spirals — each whorl, at about one fourth 

 of its height from the suture, projects in an angular carination, 

 which carries a small, but distinct rounded thread, rising into 

 transverse tubercles where it crosses the longitudinal corrugations. 

 Above this carinal thread there are four very small flat spiral 

 threads, equal, and equally parted by three small furrows, in each 

 of which lies a minute spiral thread. The furrow which separates 

 the lowest of these four spirals from the carinal thread is plain, 

 having no minute spiral in it. Below the carinal angulation the 

 whorls are constricted. Within this constriction there are on 

 each whorl two small alternating furrows and threads, then a 

 comparatively broad and deep furrow, below which a small spiral 

 thread lies immediately at the suture, but above it. It is this 

 suprasutural thread which forms the edge of the base, and is there 

 nearly as strong as the carinal thread. Its inner side is defined 

 by a strongish furrow, within which the whole base to the point of 

 the pillar is covered with small alternating threads and furrows, 

 in number about 9, of which the first and the fifth thread are a 

 little stronger than the rest. Besides these, the whole surface is 

 microscopically covered with sharpish spirals and slight lines of 

 growth. These last are very distinct toward the point of the 

 pillar. Colour brownish grey, with porcellanous white spots 

 where the spirals cross the corrugations, and with a good deal of 

 suffused ruddy brown, especially on the base and about the 

 suture ; the edge of the pillar is deeply tinged with this colour. 

 Spire pointed, conical, with straight profile lines, angulated by 

 the pagoda-like projections of the whorls at the carina, and their 

 constrictions below this into the suture. Apex small and rounded. 



