8 PROCEEDINGS OF THE ACADEMY OF [Jan., 



covering the entire surface, those above the periphery being swollen 

 at intervals, when crossed by the radial wrinkles or corrugations 

 that follow the growth lines, thus forming both the raised granula- 

 tion and the whitish spots, from the raised lirse becoming whitish 

 where swollen. The swelling of the revolving spirals becomes very 

 pronounced along the periphery, which is thus raised into a series of 

 tubercles, commencing about the beginning of the fourth whorl 

 and continuing to the lip. The swelling of the lirse to form the 

 granulation does not extend far below the periphery, not more than 

 4 or 5 of the revolving striae being thus affected. The striae continue, 

 however, to the umbihcus, becoming fainter as this is approached. 

 Diam. 7,7, alt. 5.5 mm. 



The keeled and tuberculated periphery seems to be characteristic 

 of this species, but is not always, as in this Swift Collection lot, 

 carried out to the lip. It is present in the young shells in all cases, 

 which would seem to indicate that the ancestral species must have 

 resembled this one from the Swift Collection. None of the Mande- 

 ville region specimens normally show this tuberculated and keeled 

 periphery in the adult state, at least not entirely up to the lip; 

 but the young all show it. The Somerset Road specimens (Plate 

 I, figs. 6, 10), w^hich perhaps lived under as nearly optimum condi- 

 tions for this species as any collected in the Mandeville region, 

 show this tuberculated and keeled periphery up to nearly the end 

 of the fifth whorl, but the peripheral tul^erculation dies away 

 before the sixth whorl is reached. Young shells from this station 

 have quite a different appearance from the adults. This seems, as 

 above stated, to be the general condition of the species in the Man- 

 chester region, the adult stage has lost the peripheral granulation, 

 but the younger stages show it. And it is perhaps more pronounced 

 in the Somerset specimens than in any of the others, the last whorl 

 being frequently nearly smooth (Plate I, fig. 4, figs. 7-9), on the 

 periphery. An exceptional specimen from Somerset, showing the 

 tuberculated periphery, is figured at 5 on the plate. The tuberculate 

 condition of the periphery extends from the middle of the third 

 whorl (2.5 whorls from the apex) to the middle of the fifth whorl 

 (4.5 whorls from the apex). Thus the last whorl (there are five 

 and one-half to six whorls) is comparatively smooth on the pe- 

 riphery, and, except for the color pattern, the shell at first sight 

 resembles L. aureola. The color pattern itself varies when the 

 peripheral tuberculation disappears; when it is present there is a 

 regular periodicity in the recurrence of the whitish patches which 



