REPORT OX THE GASTEROPODA. 551 



15. Bittium abruptum, Watson (PI. XLI. fig. 4). 



Cerithium (Bittium) abruptum, Watson, Prelim. Report, pt 5, Journ. Linn. Soc. Lond., vol. xv. p. 119, 



sp. 19. 



Station 75. July 2, 1S73. Lat. 38° 38' N., long. 28° 28' 30" W. Fayal, Azores. 

 450 to 500 fathoms. Volcanic mud. 



Shell. — Small, narrow, conical, blunt, in general form very like a decollated Cerithi- 

 opsis metaxoB, solid, translucent, white. Sculpture : Longitudinals — there are on the last 

 whorl about thirteen, on the earlier, fewer longitudinal ribs, which are low and narrow, 

 and are parted by flat and broader furrows. They come down the spire, from whorl to 

 whorl, with a strong twist. The embryonic whorls have ten or twelve small ribs. 

 Spirals — except on the first two whorls there are on each whorl four narrow, rounded, 

 prominent spiral threads, which rise, as they cross the longitudinals, into pointed high 

 tubercles. The furrows which part them (except that between the third and the fourth) 

 are narrower than the spirals. The highest of these spirals is the weakest and least pro- 

 minent, being pinched in by the superior contraction of the whorl into the suture. Close 

 above this highest spiral runs the suture. The base of each whorl is roundly but rather 

 abruptly contracted, so that the sutural furrow has its upper side abruptly, its under side 

 Gradually, declining. The base, which is oblique, concave, and contracted, has a strong 

 plain spiral thread round its edge, and a very minute thread encircling the top of the 

 pillar, the scar of the siphonal cut. Besides the larger systems of sculpture, there are 

 some faint and irregular traces of microscopic rounded longitudinals and sharper spirals. 

 Colour translucent white. Spire high, narrow, with very straight outlines, and scarcely 

 contracted. Apex excessively blunt and abrupt, the extreme point being rounded and 

 barely rising into view ; it is quite smooth and polished. The second whorl is longitudi- 

 nally ribbed and polished ; on the third the ordinary sculpture begins. Whorls 1 1 , convex, 

 constricted suddenly below and gradually above. Suture excessively minute and faint in 

 itself, but its place strongly marked by the constriction of the whorls above and below. 

 Mouth very small, oval, perpendicular, pointed above, and with a large open rounded 

 slit in front, whose edge is hardly reverted. Outer lip thin, advancing on the base 

 much beyond the point of the pillar. Inner lip a thin glaze, with microscopic corruga- 

 tions on the pillar. Pillar very short, with a broad top spreading out to meet the outer 

 lip, straight, the point broad but sharp. H. 0"23 in. B. # 05. Penultimate whorl, height 

 0-03. Mouth, height 0'028 ; breadth 0'02. 



This species in general aspect is very like Gerithiopsis metaxcc (Chiaje), but differs in not 

 having the sharp sculptured apex ; the whorls, in consequence of the sutural contraction, are more 

 rounded ; the longitudinals are swellings of the whole shell, not, as in that other, mere projecting 

 tubercles ; the spirals are more definitely continuous ; the longitudinal rows of tubercles run less 

 definitely from whorl to whorl, and have a strong twist as they proceed down the spire, while in 

 Cerithiopsis metaxcc their continuous lines are very straight. 



