AMPHIBOLIC^ — SIPHONARIID^. 109 



appendage of the mantle, with, in Siphonaria, a branchia in 

 addition. 



Tliree families are admitted. 



Spiral, operculate. Amphibolidge. 



Conical (limpet-like), not operculate. Siphonariidfe, Gadiniidas. 



Family AMPHIBOLID-ZE. 



Shell spiral, subglobose, operculated. 



Animal with the external features and dentition of the pulmo- 

 nata, but the respiratory cavity only communicates with the 

 free air by a small valvular opening. Aquatic, living in brackish 

 water. 



They partake of the characters both of the aquatic pulmonata 

 and of the Ampullariidse, and might be considered as related to 

 that family perhaps quite as much as to the former. 



Amphibola, Schumacher, 1811. 



Syn. — Ampullacera, Quoy, 1832. Thallocera, Swains., 1840. 



Distr. — New Zealand. A.nux-avellana^ Chemn. (ciii, 41). . 



Shell subglobose, rather thick, rugose, umbilicated ; spire 

 short, whorls shouldered above ; umbilicated ; aperture suboval ; 

 columellar lip callous ; columella flattened and reflected ; outer 

 lip sinuous posteriorly ; operculum corneous, subspiral. 



Lingual membrane large, very broad, expanded, and long, with 

 a central space or line scai'cely defined : teeth numerous, equal, 

 similar, four-sided, rather longer than broad, in straight cross- 

 lines, with a broad rounded lobe, rather more sinuous on the inner 

 than on the outer side of its front edge. Eyes sessile on the 

 front part of the cephalic disk formed by the expanded tentacles. 

 Respiratory cavity closed, except a small valvular opening on 

 the right side. 



The afiimals of this family inhabit salt marshes near the sea, 

 the living shells sometimes having Serpulse attached to them. 

 They appear to respire the free air. The Amphibolidse offer an 

 exception to the general rule, that pulmonifers with a closed 

 mantle-cavity ai'e destitute of opercula. They live in pools of 

 brackish water, and at certain seasons bury themselves in the 

 sandy mud. The New Zealanders collect and employ them as 

 articles of food. 



ampullarina, Sowb., 1842. Shell thin, globular, umbilicated; 

 spire short ; whorls rounded ; inner lip simple ; outer lip sinuous 

 in the middle. A. fragilis, Quoy (ciii, 42). 



Family SIPHONARIID^. 



Characters those of the typical genus. 



Siphonaria, Sowerby. 

 Bistr. — 90 sp. Cape, India, Philippines, Australia, New Zea- 



