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Bulimi, and on the modification of their shell to the local physical condi- 

 tions in which the species live.* It ran as follows : — 



The Bulimi are distributed over the equatorial, tropical, and warm tem- 

 perate regions of the globe in assemblages of species, limited in their 

 range, and of very distinct typical character; and being of sluggish habits 

 with few means of transport, little migration occurs even where there are 

 no such natural boundaries as seas, deserts, or mountain chains. Of the 

 Bulimi known from all parts of the world, the localities of nearly 600 

 species are now well authenticated. Their area of geographical distribu- 

 tion lies between 40° S. and 35° N. in the new world, and between 42° S. 

 and 52° to 55° N. in the old world ; — that is, between the southern bor- 

 ders of Chili and Texas in the former, and between Van Diemen's Land 

 and Germany, if not Sweden, in the latter. And there is no country 

 within this area of which the genus of snails under consideration does not 

 form part of the zoology. There is one abnormal species, B. lubricus, re- 

 moved from the genus by British authors [Zua lubrica), which obtains a 

 more northerly range and a greater elevation in both hemispheres. 



Regarding the differences of form, composition, and disposition of colour 

 in the shell, the Bulimi are distributed over this area in seven provinces, 

 comprising about forty typical assemblages of species. Of these three- 

 fifths inhabit the western hemisphere, principally Central America, and 

 two-fifths have a wider range and greater local variety of character, in con- 

 formity with the more varied arrangement of the land, in the eastern. 

 Taking the size and substance of the shell at different elevations and in 

 different degrees of temperature, it may be remarked that the calcifying 

 energies of the Bulimi are most strongly exerted in thickly wooded dis- 

 tricts, in the midst of plenty of decaying vegetable matter, close and 

 humid, with a mean heat of from 80° to 85°, among shady thickets or in 

 ravines. Near the sea-level in thin calcareous soil, and in sandy plains, 

 where the vegetation is scanty and parched, and in grassy savannahs, the 

 shell is thin and often vividly coloured. In those species whose habit it 

 is to burrow in the ground, the shell is mostly small, patternless, and of 

 glassy tenuity, even in localities remote from each other and differing ma- 

 terially in physical character. 



The Western Hemisphere comprises four grand provinces of distri- 

 bution, the Venezuelan, the Brazilian, the Chilian, and the Bolivian, and 

 from these may be further distinguished the districts of the Galapagos 

 Islands and of the Great Antilles. The first province includes the coun- 

 tries of New Granada and Venezuela ; the second comprises the empire of 

 Brazil and Buenos Ayres ; the third comprises Chili and West Peru ; and 

 the fourth province includes Bolivia and the Argentine Republic. About 

 three hundred and fifty species have been described from this hemisphere. 

 * Read before the Royal Society in 1851. 



2 P 



