92 AURICULIDA. 
isting for at least a month either under water or out of it (if the 
air is moist). 
PrroniA, 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. 
BucuanantA, Lesson, 1830. 
Distr.—Chili. B. Oncidioides, Lesson. 
Like the last genus, but mantle smooth, with a large central 
tubercle and radiating striz ; oral appendages simple, subulate, 
retractile. Lingual dentition? The type is three-and-a-half inches 
long, yet has not been seen since Lesson described it, more than 
fifty years ago. 
OrpER BASOMMATOPHORA. 
Tentacles flattened-triangular or subcylindrical, 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 GrHypRopHILA, Fer. Teguments rugose; terrestrial, 
but usually inhabiting sea-shores. 
Suborder HyGropuita, Fer. (Limnophila, Hartmann.) Tegu- 
ments smooth. Fresh water. 
Suborder THaassopHILa, 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. 
SusporpER GHHAHAYDROPHILA. 
Famity AURICULIDA. 
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, 67). 
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 usually frequenting salt marshes and the vicinity of 
