OF MOLLUSCA. 167 



■ft+'t' Shell permanently covered by the mantle ; edge acute, 

 double-grooved. 



15. PUEILLIA. 



Mantle very large, covering the foot, smooth ; foot granulated. 

 Shell conical, smooth ; anal perforation very large, subcentral ; aper- 

 ture ovate ; margin entire, with a sharp, white, thinned edge. 



1. P. apertura, t. 269. f. 5. Pupillsea aperta, Krauss, 



II. Heteroglossa. Teeth pellucid, in five to eight longitudinal 

 series, variable in form, the larger ones with opake black tips. 

 Foot without any lateral fringe. Shell symmetrical. (See 

 p. 136.) 



Suborder IV. Cirrhobranchia. 



Gills two, symmetrical, tufted on the back of the neck. Body 

 elongate-conical. Shell conical, tubular, with an apical opening. 

 Lingual membrane wide, ovate ; central series one-toothed ; lateral 

 series with one tooth ; limb laminated (p. 162). 



Fam. X. DENTALIAD^l. 



Foot small, conical ; sides simple. Body and shell elongate-coni- 

 cal ; apex pierced. 



Body cylindrical, conical. Gills : two, symmetrical, sublateral, and 

 somewhat post-centrally situated organs, having their bases fixed 

 on and hanging from the concave surfaces of the animal, with their 

 points vertically parallel to the bases ; they are united at their 

 inner surfaces by a bridle of branchial strands arranged symmetri- 

 cally. Heart at the anterior end of the branchial cavity. Vent at 

 the base of the branchial cavity under the mantle, about the middle 

 of the shell. Head rudimentary. Tentacles and eyes none. Lips 

 bearded. Mantle circular, thick, fleshy, and covering the foot in 

 front, thin posteriorly, and attached to the shell near its hinder ex- 

 tremity. Foot central, conical, with two symmetrical side-lobes 

 mounted on a long pedicel, grooved on both surfaces, centrally 

 hollowed out, the cavity communicating with the stomach. Sexes 

 probably united. Stomach with a strong anterior gizzard. Lingual 

 membrane broad, ovate, with three longitudinal series of teeth, the 

 central dentated, lateral broad. 



They live on foraminifera and small bivalves. The symmetrical, 

 subventral position of the branchise, the posterior flow of water to 

 them, and the resemblance of the foot to that of some bivalves, com- 

 bined with the similar character of its action, appear in a striking 

 manner to show its connexion with the Conchifera. — Clark, Ann. 

 Nat. Hist. ser. 2. iv. 328. 



M. Deshayes (Mem. Soc. Hist. Nat. Paris, 1828) regards the 



