246 MANtJAL OF THE MOLLUSCA. 



Stetjthiolaria, Lam. 



Etymology, struthio, an ostricli (-foot), from tlie form of its 

 aperture. 



Type, S. straminea, PL lY., Pig. 6. 



Shell turreted ; wliorls angular ; aperture truncated in front ; 

 columella very oblique ; outer lip prominent in 

 tlie middle, reflected and tldckened in tlie adult ; 

 inner lip callous, expanded ; operculum claw- 

 sliaped, curved inwards, with, a projection from 

 the outer, concave edge (Fig. 101). 



Animal with an elongated muzzle ? tentacles 

 cylindrical ; eye-pedicels short, adnate with the 



tentacles, externally: foot broad and short. 

 Fig. 101. ,-rz- \ 



Operculum of (Kiencr.) 



istruthioiaricu. Distribution, 5 species. Australia and New 

 Zealand, where alone it occurs sub-fossil. 



Family IY. — Melaniad^. 



Shell spiral, turreted ; with a thick, dark epidermis ; aperture 

 often channeled, or notched in front ; outer lip acute ; operculum 

 horny, spiral. The spire is often extensively eroded by the 

 acidity of the water in which the animals live. 



A7iimal with, a broad non-retractile muzzle ; tentacles distant, 

 subulate ; eyes on short stalks, united to the outer sides of the 

 tentacles ; foot broad and short, angulated 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. 



Melania, Lam. 



Etym,ology, melania, blackness (from melas). 



Type, M. amarula. PL YIIL, Fig. 25. 



iSynonyms, Thiara, Megerle. Pyrgula, Crist. 



Shdl turreted, apex acute (unless eroded) ; whorls orna- 

 mented with striae or spines ; aperture oval, pointed above ; 

 outer lip sharp, sinuous; operculum subspiral. PL YIIL, 

 Fig. 25.* 



Distrilmtion, 361 species. South Europe, India, Philippines, 

 Pacific Islands. Distinct groups in the southern States of 

 North America. 



