THE NAUTILUS. 105 



cave, with the margin of the whorl thickened, or raised in an incurved lamina, 

 nucleus subcentral. 



Alycxus. Operculum circular, subtestaceous, obsoletely multispiral. 

 Diplommatina. Operculum subtestaceous, thin, with few whorls, outer edge 

 with thin lamella. 



II. Operculum cartilaginous? 



Genus, Pterocyclos. Operculum subcartilaginous, multispiral, interiorly 

 concave. 



III. Operculum corneous. 



Genera, Craspedopoma^ Aulopoma, Cyclophorus, Leptopoma, Meffalomastoma, 

 Calaulus, Pupinella, Pupina, Registoma, CalUa. 



Craspedopoma. Operculum horny, solid, closely whorled. Nucleus central, 

 external lamina plane, internal furnished in its last whorl with a circular 

 prominence, centre profoundly concave. 



Aulopoma. Operculum horny, arctispiral, planorbal composed of two laminae, 

 with an intermediate channel, with the last whorl furnished interiorly with a 

 circular groove. (The outer edge larger than the aperture and reflexed over 

 the peristome of the shell. Adams.) 



Cyclophorus. Operculum horny, thin, arctispiral, externally more or less 

 concave. 



Leptopoma. Operculum membranous, arct'spiral, flat. 



Megalomastoma. Operculum subcircular, thin, horny, arctispiral, planular. 



Calaulus. Operculum orbicular, plane, corneous, arctispiral. 



Pupinella. Operculum horny, arctispiral. 



Pupina. Operculum thin, membranous, arctispiral, subplanum. 



Rcgistoma. Operculum circular, thin, horny, arctispiral. 



Callia. Operculum thin, membranous, arctispiral. 



{To be continued.) 



NOTES. 



HELIX HORTENSIS ON MAGDALEN ISLAND In 1901 the Car- 

 negie Museum of Pittsburg sent an expedition to the Magdalen 

 Islands and Labrador to collect birds and eggs, and on June 23d, 

 while at Grand Entry, Magdalen Island, one of the party collected 

 a lot of Helix hortensis Miill., which show a remarkable tendency 

 towards a single type of banding. There are about 330 shells in the 

 lot, counting young and old, and all are the form with yellow ground. 

 The following table, based on matured shells only, gives the number 

 of each form : 



18612345. 

 48 (12)345. 



