OCR Text |
Show 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 -^0 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, tbe 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 ; sliglitly sinuated from the forward advauce 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. |