REPORT ON THE GASTEROPODA. 553 



17. Bittium aedonium, 1 Watson (PI. XLI. fig. 6). 



Cerithium (Bittium) aedonium, Watson, Prelim. Report, pt. 5, Journ. Linn. Soc. Lond., vol. xv. p. 121, 



sp. 21. 



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

 100 to 150 fathoms. 



Shell. — Small, narrow, conical, blunt, with faintly convex outlines, which are deeply 

 broken at the sutures, rather abruptly truncate at the base, reticulately tubercled, solid, 

 translucent, glossy, white. Sculpture: Longitudinals — there are on the last whorl 19 rows 

 of small, narrow, but longish, rounded, rather coarse tubercles, parted by furrows, which are 

 shallow, rather unequal, and fully broader than the ribs. There are over the whole 

 surface fine irregular lines of growth, which are, as usual, strongest on the base. Spirals — 

 on all but the first two whorls there are three spiral threads, which rise into tubercles as 

 they cross the longitudinals ; they are parted by deep narrow furrows ; of these three the 

 two lower are strong, the upper of the two being a little the stronger and more prominent. 

 The third and highest spiral is not materially smaller than the others, but is much less 

 prominent, the whole whorl being at this part constricted. The suture hes immediately 

 above this spiral. Beneath the lower spiral the whorl is sharply constricted, and a very 

 minute plain spiral lies in the bottom of the furrow and immediately above the suture : 

 this minute spiral is the edge of the strongish spiral which encircles the base. Round the 

 top of the pillar is a minute sharp spiral thread, which runs round the back into the 

 columellar canal. There are microscopic spirals over the whole surface. Colour pure 

 translucent white. Spire is high and narrow : its outlines, which are a good deal inter- 

 rupted by the sutural constriction, are slightly convex. Apex, of 1^ whorls, is tumid, 

 bluntly rounded, a little oblique, and glossy white. Whorls 9, rounded, contracted above 

 and constricted below. The base is rather truncate and rounded. Suture very minute, 

 but well indicated by the broad open furrow in which it lies. Mouth oval, little pointed 

 above, with a small well-rounded canal at the pillar. Outer lip sharp, scarcely incurved 

 above, not prominent, but patulous below, angulated at the corner of the canal, round 

 which it is scarcely reverted. Pillar straight, prominent, and pretty strong, with a sharp 

 twisted edge at its point. Inner lip a mere glaze on the body, but forming a thin 

 distinct edge along the length of the pillar. H. 0*17 in. B. - 057. Penultimate whorl, 

 height 0-032. Mouth, height 0-039, breadth 0-025. 



This species is more like Bittium cinctum, Watson, and Bittium depaupcratum, Watson, than 

 anything else I know. These are both Madeiran species. Its whorls are much more rounded than 

 in either of these. The base is not produced into a rounded cone as in Bittium cinctum, Da Costa,, 

 but is rather abruptly truncate and very slightly contracted ; it is also plain, and has not the spiral 

 threads which appear on these two species. The contraction of the whorls into the suture makes 



1 &j)3o'»;of, belonging to a Nightingale. 



(ZOOL. CHALL. EXP. — PAKT XLII. — 18S5.) Tt 70 



