156 PLEUROTOMIM. 



Genus BELA (Leach), Gray, 1847. 



Shell usually thin and white, fusiform; spire elongated, 

 turreted ; canal short, straight, truncated below ; columella 

 simple, flattened ; lip thin, the sinus absent or barely indicated. 

 Operculum oval, pyriform, with apical nucleus, 



Foot truncated or bilobed in front, drawn out behind ; ten- 

 tacles cylindrical, rather short, the eyes external at the middle 

 or three-fourths of their length. Teeth straight ( 1-0-1 ) ; Plate 

 33, figs. 55, 52. 



Distr. Northern Seas. 



The following may be considered sections : 



Section TYPHLOMANGILIA, Sars., 1878. Animal blind. 



Section H^EDROPLEURA, Monterosato, 1883. Shell not turricu- 

 lated, with a few strong longitudinal ribs. Mediterranean. 



Section ETALLONIA, Desh., 1862. This eocene group is here 

 included by Dr. Fischer. I have placed it in the family Aplus- 

 tridse (S. and S. Conch., ii, 362). 



Subgenus BELOMITRA, Fischer, 1882. 



Shell elongated, with mammillary apex; aperture oblong; 

 lip sinuous, slightly concave towards the suture ; columellar lip 

 with several small but strong plications ; canal short. Operculum 

 with apical nucleus. 



Genus LACHESIS, Risso, 1826. 



Shell small, strong, turreted, many-whorled, the last whorl 

 not very large ; surface sculptured by longitudinal ribs and 

 revolving striae ; apex mammillated ; aperture oval ; canal very 

 short, straight, not recurved ; outer lip slightly thickened exter- 

 nally, crenated within, without apparent sinus. Operculum 

 unguiculate. 



Animal with diverging tentacles, short siphon, and short ovate 

 foot ; the eyes on stalks connate with, and at half the length of 

 the tentacles. 



I retain the above name, although previously used by Daudin 

 in reptilia and by Savigny in arachnida. One of its synonyms, 

 Nessea, Risso, was also used by Lamarck for a genus of Polyps, 

 and by Leach in Crustacea. On these accounts the group has 



