92 AURICULID^. 



isting for at least a month either under water or out of it (if the 

 air is moist). 



Peronia, Blainv., 1824. 



Syn. — Onchis, Fer., 1821. Oncus, Ag. 



Distr. — Shores of tropical seas. P. punctata^ Quoy (cii, 69). 



Animal elongate-ovate ; like the last genus, but with arbusculi- 

 form tufts and tubercles on mantle. Littoral. 



BucHANANiA, Lesson, 1830. 



Distr. — Chili. B. Oncidioides, Lesson. 



Like the last genus, but mantle smooth, with a large central 

 tubercle and radiating strise ; oral appendages simple, subulate, 

 retractile. Lingual dentition ? The type is three -an d-a-half inches 

 long, yet has not been seen since Lesson described it, more than 

 fifty years ago. 



Order BASOMMATOPHORA. 



Tentacles flattened-triangular or subcjdindrical, contractile 

 (but not invertible) ; eyes at their bases, sessile. 



Shell usually covered by a corneous epidermis and oblong, 

 few whorled, without operculum. Mostly aquatic or littoral. 



Suborder Gehydrophila, Fer. Teguments rugose ; terrestrial, 

 but usually inhabiting sea-shores. 



Suborder Hygrophila, Fer. (Limnophila, Hartmann.) Tegu- 

 ments smooth. Fresh water. 



Suborder Thalassophila, Gray. Head a flattened disk, ap- 

 parently resulting from the union of the tentacles to the skin of 

 the head ; inhabiting sea-shores and brackish water. 



Suborder GEHYDROPHILA. 

 Family AURICULIDJE. 



Shell spiral, covered by an epidermis, solid, usually thick; 

 spire more or less elevated ; whorls sometimes flattened ; aper- 

 ture elongated, contracted by columellar teeth, and often also by 

 teeth within the lips. 



Lingual membrane broad and elongated ; teeth numerous, in 

 slightly bent cross-series ; central tooth equilateral, narrow, tri- 

 cuspid ; lateral and marginal teeth also tricuspid, rather inequi- 

 lateral, diminishing in size towards the outer edge (xiii, 61). 

 Head ending in a snout ; mouth with a horny lunate upper jaw, 

 and with two dilated buccal lobes, united above, separate below; 

 tentacles subcylindrical, contractile ; eyes sessile at the inner 

 sides of their bases. Mantle closed, with a thickened margin ; 

 respiratory orifice posterior, on the right side. Sexes united. 



Animal usuall}^ frequenting salt marshes and the vicinity of 



