MA.EIKE MOLLUSCA OP MADEIRA. 249 



however, from the suture a good way downwards present them- 

 selves as well-defined rounded curved riblets parted by narrower 

 but open furrows ; these riblets cease rather suddenly and pass 

 into very faint lines of growth. Spirals none. Colour porcel- 

 lanous white, somewhat translucent except rouiid the whorls 

 below the suture ; below this dead-white band lies a broadish 

 smoky-brown band, which in the upper whorls encircles their 

 base ; in the body-whorl below this dark band a white band of 

 about the same breadth occupies the periphery ; below it on the 

 base is a slightly narrower dark band ; the whole base round the 

 umbilicus is white, but there is often a rusty tinge in the 

 umbilicus and on the edge of the umbilical pad ; there are colour- 

 variations from uniform pure white to dark brown, with a pale 

 base, but the spire has always a dark tinge. Epidermis : there 

 are traces of a hard, corneous, yellowish-brown iutegument. 

 Spire unusually small, but well-exserted and with a minute 

 prominent dark tip. Whorls 4|, not in the least angulated or 

 gibbous ; those of the spire are unusually small ; the body-whorl 

 is large, and gives breadth to the shell in spite of being longitudi- 

 nally and obliquely drawn out. Suture scarcely oblique, linear. 

 Ifouth semi-oval, open, long rather than large, the whole plane 

 of its edge retreats extremely from above to the base ; its height 

 is nearly four-fifths of the whole height of the shell. Outer lip 

 thin, well arched, retreating to the base, but from that point 

 advancing slightly to the pillar. Inner lip oblique, nearly 

 straight, thickened by a broad white porcellauous pad which 

 fills the whole upper corner of the mouth, projecting there in a 

 blunt, low, rounded prominence ; the face of this pad projects 

 bluntly all the way to the point of the pillar, it crosses the body 

 with a straight well-defined edge whose direction is obhque; 

 where it quits the body to join the rust-stained umbilical pillar- 

 pad it is more or less deeply cut by the umbilical furrow which 

 sometimes feebly, sometimes very strongly, twists out round the 

 pillar, circumscribing it markedly but failing to cut in on the 

 edge of the inner lip, which here to the point of the pillar is 

 shortly reverted and slightly thickened. Umbilicus is sometimes 

 a mere depression, but normally is a strong but rather narrow 

 furrow coiling round the pillar and deeply penetrating the 

 middle of the shell. Operculum calcareous, pure white, pretty 

 strong, lustrous, fairly flat, but slightly padded in the nuclear 

 region, from which a very slight rounded swelling curves with 



LIKN. JOUBN. — ZOOLOGY, VOL. XXVI. 19 



