GASTEROPODA. 289 
Distribution, including the sub-genera, above 1,600 species 
(several hundred species are undescribed). World-wide ; rang- 
ing northward as far as the lmit of trees, and southward to 
Tierra-del-Fuego, but most abundant by far in warm and humid 
climates. M. D’Orbigny observed 6 species at elevations ex- 
ceeding 11,000 feet in South America, and Layard found Z. 
gardenert at the height of 8,000 feet in Ceylon. The species of 
tropical and southern islands are mostly peculiar. Several of 
the smaller British species, and even the large garden-snail (ZZ. 
aspersa), have been naturalised in the most remote colonies. 
The Neapolitans and Brazilians eat snails. 
Fossil species about 200. Hocene—. Hurope. 
Sections: Acavus, Montf. Shell imperforate. H. heemastoma, 
ee LT,, Hig. 1. 
Geotrochus (lonchostoma) Hasselt, Trochiform, flat beneath. 
Polygyra, Say. Depressed, many-whorled. H. polygyrata, 
Peele, His, 2. - 
Tredopsis, Raf. Aperture contracted by tooth-like projections, 
i Harsuta, Pl. XTI., Fig. 5. 
Carocolla, Lam. Peristome continuous. H. lapicida, Pl. XTII., 
Fig. 3. 
Sub-genera. Anastoma, Fischer. (Tomigerus, Spix.) H. 
globulosa, Pl. XII., Fig. 4. Aperture of adult turned up- 
“ wards, ringent; 4 species. Brazi.. 
Hypostoma (Boysii), Albers, is a minute Indian snail, in which 
the aperture is similarly distorted. 
Lychnus (Matheroni, Req.) has a similar shell, but no apertural 
teeth ; 3 species occur in the Hocene Tertiary of South France. 
Streptaxis, Gray. TH. contusa, Pl. XII., Fig. 6. Sub-globose, 
lower whorls receding from the axis of the upper; 84 species. 
Brazil, West Africa, Mascarene Islands, South Asia. 
Sagda, Beck. H. epistylium, Pl. XII., Fig. 7. Imperforate, 
globosely conoid, close-whorled, aperture lamellate within, lip 
sharp; 3 species. Jamaica. 
Prosérpina (nitida), Guilding. Shell depressed, shining, 
callous beneath ; aperture toothed inside; peristome sharp. 
Distribution, 6 species. Jamaica, Cuba, Mexico. 
Fossil, Hocene—. Isle of Wight. (EF. Edwards.) 
Helicella, Lam.* Type, H. cellaria, Pl. XTI., Fig. 8. Shell 
thin, depressed ; peristome sharp, not reflected. Lingual edgo- 
tecth aculeate. 110 species. 
Stenopus (cruentatus), Guild. 
* For this group Dr. Gray formerly employed the name Zonites, given originally by 
Montfort to Helix Algira; in his later works he adopts Z/elicella. 
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