Gasteropodom Mollusca into larger Groups and Families. 129 



sunk into the foot ; eyes none ; operculum distinct, spiral, few- 

 whorled (fig. 7). 



a. Operculum, outer layer shelly. Natica. 



b. Operculum simple, horny. Neverita, Polinices, Mammilla, 

 Stomatia. 



From Dr. Loven's description of the animal of Trichotropis 

 borealis, it should be referred to this suborder, and equally so by 

 Messrs. Forbes and Hanley's figures, t. II. f. 1 ; but in examining 

 the animals of Trichotropis bicarinatus, the original type of the 

 genus, I find the animal to have a rostrum and no proboscis. I 

 should have been inclined to have regarded the animal of these 

 two species as probably forming two genera, but Messrs. Forbes 

 and Hanley's description of the animal (Brit. Moll. 361) agrees 

 pretty well with the animal of T. bicarinatus. 



F. Ptenoglossa. Teeth on lingual membrane in many series, 

 numerous, similar (fig. 8). 



Fam. 14. CASsioiDiE. Mantle en closed, with a recurved siphon; 

 shell ventricose, subglobose, with a recurved canal, often variced ; 

 outer lip thickened ; lingual membrane short, broad, triangular, 

 with many rows of similar lancet-shaped teeth, and a single 

 small dentated tooth in the central series ; operculum annular ; 

 nucleus in the middle of the straight inner side. Bezoardica, 

 t Cassis, ?Levenia, t Mario. The teeth bear no resemblance to 

 those figured by Quoy and Gaimard as those of Bezoardica. 



Fam. 15. ScALARiADiE. Foot moderate, mantle enclosed; 

 shell turrited, variced, without any canal ; eyes on outer side of 

 the subulate tentacles ; operculum horny, spiral. Scalaria. 



Fam. 16. Acteonid^. Foot moderate ; mantle enclosed ; eyes 

 on the inner side of the base of the expanded tentacles ; oper- 

 culum horny, subspiral. Acteon. 



G. Gymnoglossa. Teeth and lingual membrane rudimentary 

 or none. 



Fam. 17. AcusiUiE. Foot small; mantle enclosed, with an 

 elongated siphon ; shell turrited ; lip thin, not variced ; eyes on 

 tip of tentacles or wanting ; tentacles very small or wanting ; 

 operculum annular; nucleus apical. Acus (tentacles small). 

 Subula (tentacles and eyes none). Leiodomus (suture callous ; 

 operculum ovate ; tentacles small ; has been confounded with 

 Bullia). 



Fam. 18. PyramidelliDjE. Foot moderate ; mantle enclosed ; 

 eyes on the inner side of the broad folded tentacles ; operculum 

 horny, spiral; shell spiral, pillar plaited. 



Ann. 5f Mag. N. Hist. Ser. 3. Vol. xi. 9 



