130 MANUAL OF THE MOLLUSCA. 



branchial plume single, long ; lingual ribbon linear ; teeth single, hooked^ 

 denticulated ; uncini 3, the fii'st transverse, 2 and 8 claw-shaped. 



■^^^ ^^x^ 



Fig. 80.* 



Distr., 3 sp. Labrador, Norway, Brit., Medit. W. Africa. Range, — 

 100 fms. 



Fossil ; see Pteroceras and Rosiellaria ; above 200 species, ranging from 

 the lias to the chalk, probably belong to this genus, or to genera not yet 

 constituted. 



Struthiolakia, Lam. 



Etijm., struthio, an ostrich (-foot), from the form of its aperture. 



Type, S. straminea, PL IV., fig. 6. 



Shell tun-eted ; whirls angular ; aperture truncated in front ; columella 

 very oblique ; outer lip prominent in the middle, reflected and thickened in 

 the adult; inner lip callous, expanded; operculum claw-shaped, curved in- 

 wai'ds, with a projection from the outer, concave edge. 



Animal with an elongated muzzle ? tentacles cylindrical ; eye-pedicels 

 short, adnate with the tentacles, externally ; foot broad and short.. (Kiener.) 



Distr., 5 sp. Australia and New Zealand ; where alone it occurs sub- 



FAMILY IV. IMelaniad^. 



Shell spiral, turreted ; mth a thick, dark epidermis ; apertm'e often 

 channelled, or notched in fr-ont ; outer lip acute ; operculum horny, spii-al. 

 The spire is often extensively eroded by the acidity of the water in which the 

 animals live. 



Ammal with a broad non-retractile muzzle ; tentacles distant, subulate ; 

 eyes on short stallcs, united to the outer sides of the tentacles ; foot broad and 

 short, ang-ulated in front ; mantle-margin fringed ; tongue long and linear, 

 with a median and 3 lateral series of hooked multi-cuspid teeth. Often 

 viviparous. Inhabiting fresh-water lakes and rivers throughout the warmer 

 parts of the world. Only fossil in Britain. 



^ Fijr. 80. Aporrhais pes-pelecani, L., from a drawing by Joshua Alder, Esq., in 

 the " British Mollusca." 



