151 



4f, well rounded, with a deep suture at the upper whorls, and a 

 moderate one above the last whorl. Aperture, subcircular, diam. 

 0*34, expanding rather on the umbilical than on the opposite side, 

 slightly detached from the body-whorl ; angular above. Peri- 

 treme, slightly sinuate. Umbilicus, narrow, greatest breadth 0*15, 

 least breadth 0"13. Umbilical keel, well produced. Operculum, 

 small (diameter 0"25) with spiral lamina of 9 whorls, and perhaps 

 more ; much more concave than in C. varians, and less so than 

 C. corrugatior ; planulate beneath. Height # 6, greatest breadth 

 075, least breadth 0'58. 



§ III. 



C. seminudus, Ad. See Ad. Contrib. Conch., pp. 143, 146 ; 

 Cat. Phan., p. 15. 



In order to carry out my views as to the specific value of the 

 opercula, it is necessary I should enlarge upon Adams's descrip- 

 tion, which is as follows : — " Operculum quite concave, with 

 the spiral lamella scarcely elevated, but much thickened and 

 appressed on the exterior side." My description is : — Oper- 

 culum concave on the upper side, and convex on the under side, 

 with 5 or 6 distant whorls of spiral lamina, scarcely elevated, and 

 much thickened ; the margins spreading widely outwards horizon- 

 tally into a surface covered by excentric lines, so as to join each suc- 

 ceeding whorl, and apparently not detached ; closely appressed to the 

 plane, though in reality (as seen on breaking the operculum in half) 

 not soldered to it. This operculum, from its centre, represents the 

 base of an amphitheatre, each whorl resembling very broad steps or 

 seats rising towards the exterior ; greatest diameter - 34, least 

 breadth 032. Umbilicus, greatest breadth 0*41, least breadth 0*34. 

 Habitat, north-west border of Manchester, and Bogue estate, St. 

 Elizabeth. 



C. De Burgh^eanus, Chitty. 1 Westmoreland. 



Form, globose-conic. Colour, bluish-white, with an epidermis, light 

 brick-red, on the upper whorls, turning into a pale straw-colour for 

 about ^-th below the suture, on part of the penult, and on the last 

 whorl, and rich red-brown over the remainder, which is sometimes in- 

 terrupted by straw-coloured bands at the periphery and round the um- 

 bilical keel. Sculpture, lines of growth on 3 1 of the upper whorls, 

 thence it becomes finely corrugated below the suture on the penult 

 whorl, very coarsely so on the last whorl, sometimes extremely so, 

 and knotted at the sinuation in the peritreme, all below being smooth 

 and shining, except for the continuance of the lines of growth, a few 

 distant blunted spiral lines, and a few pittings scattered below at the 

 junction of the umbilical keel and aperture. Within the umbilicus, 

 the lines of growth are very coarse. Spire, well elevated with con- 

 vex outlines. Whorls, 5, well rounded with a well-impressed suture. 

 Aperture, rather oblique, well expanded below. Peritreme, light- 

 brown, more sinuate above than C. seminudus, and sometimes very 



