366 MR. R. B.WATSON ON MADEIRAN MOLLUSKS. [Mar. 18, 



are three, on the third two (on this whorl both the longitudinal 

 and spiral threads are smaller relatively to the size of the whorl than 

 on the others). All these markings are abruptly cut off by a cross 

 line, above which is the embryonic 1 \ whorl, having a series of quite 

 independent spiral threads, four (on the extreme apex six) in 

 number, and y^ inch apart. 



Besides these markings, the whole surface of the shell when very 

 fresh may be seen to be covered with very faint and superficial spiral 

 striolations ; but these are rarely visible. There are also a good 

 many irregular and much coarser, but still very faint longitudinal 

 markings. Both of these can be best seen on the labial varix ; 

 they produce a slight frosted appearance. 



Colour yellowish or faintly brownish white, with two broad spiral 

 bands of colour, the higher and broader extending from the suture, 

 and including the two upper spiral threads, the lower including the 

 two spiral threads below the periphery ; between these two bands 

 of colour one spiral thread with its intersectional knobs stands 

 strongly out in the yellowish-white colour of the shell. On the 

 penultimate whorl, the upper edge of the lower band of colour just 

 shows in the suture ; on the superior whorls the two upper spiral 

 threads are coloured, the lower one is pale. The first two whorls 

 are uncoloured. On the labial rib, the end of each spiral thread is 

 coloured : when fresh, this colour is an exquisite brilliant crimson ; 

 but it soon fades to a ruddy brown. The whole pillar and the 

 interior of outer lip are opaque white. 



Spire elongated, conical, ending in blunt round point. 



Whorls 5 to 6, almost perfectly flat, of very gradual increase. 

 The extreme tip of the embryonic whorl is slightly turned in ; so that 

 the apex of the shell is formed by a somewhat more advanced part 

 of the first whorl. 



Suture straight, rather deep, and very strongly marked, being 

 broad and trough-like ; the underside of the trough is perpendicular 

 to its bottom line, the upperside slopes in. 



Mouth white, obliquely set, pear-shaped, flattened across the 

 belly ; small, with a slight sinus at the upper corner excavated out 

 of the thickness of junction of outer lip and body, very slightly 

 expanded towards the lower outer corner. No teeth within the lip. 



Outer lip thickened by the strong labial rib ; straight above, well 

 rounded in its basal sweep ; slightly sinuated from the forward 

 advance of the lip at lower outer corner. On its forward edge the 

 margin is pretty broad, flat or slightly hollowed into a groove, 

 longitudinally striated, and bears a sharp projecting flange on its 

 inner side forming the extreme mouth-edge. This flange takes its 

 rise on the inner side of the sinus formed at upper corner of mouth, 

 and sweeps all round, till at the point of the pillar it gradually 

 coalesces with the outer lip-margin, and the two thus united become 

 the edge of the pillar. 



Inner lip white, thin, a very little reflected, slightly projecting 

 from the thick and heavy pillar so as to leave a narrow chink, 

 faintly continued across the body. 



