xassa. 347 



the corners produced in front, and smooth-edged on each side ; 

 uncinus having a plain shaft. (Loven.)] 



Shell having a broad base, thick, opaque, nearly lustreless : 

 sculpture, strong, but not prominent, and slightly flexuous lon- 

 gitudinal ribs, of which there are from 15 to 20 on the body- 

 whorl, 20 to 2d on the penultimate whorl, and nearly as many 

 on the next whorl, the number gradually decreasing on the 

 upper whorls ; these ribs are crossed by rather deep and wide 

 spiral striae, 12 to 15 encircling the body- whorl (besides those 

 at the base), 6 the penultimate, 5 the antepenultimate, and 4 

 each of the preceding whorls, except those constituting the 

 apex, which are quite smooth and glossy ; the basal portion is 

 separated from the rest of the body- whorl by a broad groove 

 (as if pinched up), and has half a dozen spiral ridges : a tu- 

 bercular decussation is produced by the intersection of the ribs 

 and striae ; the whole surface is also covered with fine micro- 

 scopic spiral lines : colour buff, with a narrow band of purplish- 

 brown below the suture on each whorl, and now and then 

 traces of a broader band in the middle of the body-whorl and 

 of another at the base, which are discernible only near the 

 outer lip ; fresh specimens are more or less distinctly marked 

 with fine thread-like spiral lines of yellowish-brown, some of 

 which are interrupted and form rows of spots ; in such cases 

 the number of these lines or rows is from two to four on each 

 ridge; the mouth is white: epidermis extremely thin and 

 membranous : spire rather short, ending in an abrupt point : 

 apex formed of the two first whorls, and nipple-shaped : whorls 

 10, the last or body- whorl more convex than the others, but 

 compressed towards the suture ; the body-whorl occupies about 

 two-thirds of the shell : suture slight : mouth irregularly oval : 

 length (including the canal) about five-twelfths of the shell : 

 canal rather narrow, obliquely turning to the left, and ending 

 in a remarkably deep notch, which is very conspicuous when the 

 shell is placed mouth downwards : outer lip squeezed in and 

 acute- angled above, curved in the middle and below, with a 

 thick edge which is scalloped at the bottom ; inside thickened, 

 and regularly fluted with from 8 to 12 tooth- like processes : 

 inner lip forming a fine enamel, which is spread over a consi- 

 derable part of the underside of the shell and folded behind 

 the pillar ; it is more or less tuberculated, one tubercle or tooth 

 being more prominent and placed near the upper angle of the 

 mouth : pillar nearly semicircular, furnished at the base with 

 a retired flexuous fold or plait : operculum ear-shaped, light 



