ADEORBIID^E. 13 



Subgenus TEACH YDOMIA, Meek and Worthen. 1866. 



Whorls regularly ornamented with small tubercles. N. NODOSA, 

 Meek and Worthen. Carboniferous. Illinois. 



Included in Naticidse (vol. viii, 8), but is better placed here 



FAMILY ADEORBIID^. 



Shell umbilicated, auriform, depressed, paucispiral, with oblique, 

 entire aperture, simple columella, and rounded, sharp outer lip. 

 Operculum corneous, paucispiral, with excentric nucleus. 



Animal differing from Trochidse by having no cirriform appen- 

 dages of the foot. Dentition unknown. 



In this group are provisionally included a few small shells, the 

 relationships of which remain somewhat obscure. 



Genus ADEORBIS, S. Wood. 1842. 



Shell depressed, 'flattened below, white, subtrauslucent, paucis- 

 piral, periphery angulated, widely umbilicated: aperture oblique, 

 angular behind, lip sharp, not continuous. 



Europe, Japan, Philippines, West Indies, etc. A. SUBCARINATUS, 

 Mont. 



Genus ARCHYT^EA, Costa. 1869. 



Turbinated, but little elevated, thin, widely and deeply umbili- 

 cated, very finely decussated, appearing smooth, aperture rounded, 

 with sharp, simple lip. Operculum corneous, smooth and flattened 

 exteriorly, the spire slightly prominent in the centre of the inner 

 side. A. DELICATUM, Phil. Norway. 



Traehysma, Jeffreys, 1878, is a synonym. 



Subgenus PSEUDORBIS, Monts. 1884. 



Scarcely umbilicated, aperture circular, surface spirally costate, 

 not cancellated. A. GRANULUM, Brugn. Mediterranean. 



