MARGARITA. 433 



Ex\ T. Norrissii, Soirerbi/, pi. 49, fig. 5. Operculum, 

 T. Norrissii, fig. 5, a, 5, b. 



The operculum in this genus is remarkable for having 

 the outer edge of each spiral volution free and membran- 

 ous, with the margin curled. The axis of the shell is 

 widely perforated, the spire is obtuse, the columella 

 simple, and the whorls are smooth. 



Genus MARGARITA, Leach. 



Shell thin, usually without any colouring, globosely 

 conoidal, umbilicated, whorls rounded, smooth or trans- 

 versely striated ; a^oerture nearly circular; columella end- 

 ing in a simple point. 



Ex. M. helicina, Fabricius, pi. 49, fig. 6. Operculum, 

 M. helicina, fig. 6, «, 6, b. Shell, M. helicina, fig. 6, c. 



The species of this genus are principally inhabitants of 

 the shores of northern countries ; they may be distin- 

 guished from Gibbula by the whorls being simple and 

 rounded, and by the circular aperture, the interior of 

 which is often brilliantly iridescent. 



Species of Margarita. 



acuminata, Son-. costellata, Sow. 



argentata, Gould. Cumingii, A. Adams. 



aspecta, A. Adams. dilecta, A. Adams. 



balteata, A. Adams. helicina, Fair. 



biangulosa, A. Adams. Hillii, Forbes. 



calostoma, A. Adams. glauca, Moll. 



carinata, A. Adams. Gronlandica, Chem. 



cinerea, Couth. ligata, Gould. 



cingulata, A. Adams. Magellauica, Gould. 



coarctata, Migh. minutissima, Migh. 



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