542 [THE VOYAGE OF H.M.S. CHALLENGER. 



5. Bittium amblyterum? Watson (PI. XXXIX. fig. 6). 



Cerithium {Bittium) amblyterum, "WatsoD, Prelim. Report, pt. 5, Journ. Linn. Soc. Lond., vol. xv. 



p. 108, sp. 8. 

 „ gracile, Gwyn Jeffreys, "Lightning" and "Porcupine," Moll. Proc. Zool. Soc. Lond., 1885, 

 p. 54, sp. 4, pi. vi. fig. 3. 



Station 75. July 2, 1873. Lat. 38° 38' N., long. 28° 28' 30" W. Fayal, Azores. 

 450 fathoms. Volcanic mud. 



Habitat. — From North of the Bay of Biscay to the North-West of Africa in from 681 

 to 1261 fathoms (Jeffr.) 



Shell. — In general aspect very much like Bittium mctula (Loven), but narrower, and 

 having a sharper apex, and in texture and ornamentation recalling an Odostomia of the 

 CJiemnitzia group. Sculpture : Longitudinals — there are on the last whorl twenty-one 

 small longitudinal ribs, which run more or less continuously straight up the spire ; they 

 are curved so as to be posteriorly convex, and each bears two tubercles — one, the smaller, 

 near the top, the other near the bottom of the whorl ; their interstices are shallow, flat, 

 and narrow. There are, besides these, faint lines of growth, which, on the base, are 

 curvedly radiating and strong. Spirals — there is a spiral thread near the top of each 

 whorl, connecting the upper series of tubercles, and the adjacent tubercles at the lower ends 

 of the ribs are confluent, forming a continuous spiral ; round the edge of the base is a fine 

 round carinal thread ; of microscopic spirals there seems to be no trace. Colour trans- 

 lucent white. Spire high, narrow, and conical. Apex small, glossy, roundly pointed and 

 oblique, the extreme point rising slightly on one side. The embryonic whorls are two, 

 slightly oblique, convex and perfectly smooth, but for some very faint spiral scratches. 

 After these faint and sparse riblets begin to appear, and only after two more whorls do 

 these reach distinctness. The second, though narrower, is higher than the third. Whorls 

 12, of very gradual increase, flat on the sides, slightly carinated by the projection of the 

 lower thread of tubercles, a little contracted into the suture, on the base scarcely convex 

 but conical. Suture linear and very minute. Mouth squarish, with a largish oblique 

 opening into the canal, which is semicircular, a little oblique, and with very shortly 

 reverted edge. Outer lip thin, straight, but strongly angled at the corner of the base. 

 Pillar very short, perpendicular, rather broad, rather sharp-edged at the point, where 

 it is obliquely truncate and tilted to one side. Inner lip a very thin layer of glaze. 

 H. 0-25 in. B. 0-065. Penultimate whorl, height 0-03. Mouth, height 0-033, breadth 

 0-027. 



While the general form of this species resembles Bittium metula (Loven), the sculpture is very- 

 distinct, and the apex, though blunt, is much finer and sharper, and not inflated as in that species. 



1 utifiXi/Tigog, rather blunt. 



