384 MR. R. B.WATSON ON MADEIIIAN MOLLUSKS. [Mar. 18, 



Spiral threads on the base 5-6, very faint and shallow ; the lowest 

 two close to the pillar are sometimes a little stronger than the others ; 

 of these a very doubtful trace sometimes appears above the peri- 

 phery. On the upper part of the whorls near the suture a multitude 

 of very sharp, minutely microscopic, superficial spiral frettings are 

 visible. The 1| whorls are embryonic, and have an independent set 

 of very fine, microscopic spiral lines, about seven in number. 



Colour fundamentally a yellowish white, of a horny transparency ; 

 but in fresh shells this is so tinged with a suffused rich chestnut 

 that the fundamental colour only shows through on the base 

 (where it appears as a broad band) and, somewhat less purely, in 

 a band above the periphery, which band is visible on the penulti- 

 mate whorl, but disappears higher up, so that the upper whorls are 

 of a uniform pale chestnut. There are thus on the body-whorl a 

 chestnut band close to the suture, a narrow clear band below this, 

 a broad chestnut band at the periphery, and a clear whitish band 

 occupying the whole base except the centre and belly-lip, which are 

 stained with a deeper and richer chestnut than any other part except 

 the suture behind the lip, which is also very dark. In the dead shell 

 this chestnut has a great tendency to fade. In rare instances (two 

 among some hundreds) these chestnut bands on the body-whorl 

 show a tendency to break up into spots, large and squarish near the 

 suture, longer and inclined to part in the middle in the peripheral 

 band. In the full-grown shell the lip-edge is generally occupied by 

 a broad clear white band. 



Spire short and above the body-whorl attenuated, terminating in 

 a small but blunt round top. The contour-lines of the right and 

 left sides of the shell are very dissimilar, the right being very flat, 

 while the left is immensely arched. 



Whorls 4-5, slightly rounded ; the last is disproportionately large 

 and ventricose. 



Suture a mere scratch, being the less distinct from the extent to 

 which the lower whorl laps upon that which precedes it ; defined by 

 a remote (generally) dark brown line, produced by the shining through 

 of the preceding whorl. 



Mouth oval, across the belly a good deal flattened, above very slightly, 

 but at last very sharply pointed, large and a little patulous all round. 



Outer lip thin, transparent white (though sometimes the brown 

 bands advance up to the very edge), with a free continuous sweep all 

 the way round. 



Inner lip stained with intense brilliant chestnut; on the umbilicus 

 a little reflected, so as to leave behind it a very narrow but not shal- 

 low chink; carried across the belly by a rather thickish callus, which 

 is a little bevelled outwards. 



Operculum extremely thin and smooth, with scarcely any trace of 

 circular divergent lines, but with one strong longitudinal line parallel 

 to the inner margin. 



