94-8 



species occur." By Lovell Reeve, Esq., F.L.S. Communicated by 

 Gideon Algernon Mantell, Esq., LL.D., F.R.S. 



The preparation of a monograph of the terrestrial genus Bulimus 

 having enabled the author to collect good authentic data concerning 

 the localities and circumstances of their habitation, this memoir 

 embodies his observations on their general distribution under types 

 and provinces of types, and on the relation between the substance 

 and colouring of the shell, and the differences of vegetation, tempe- 

 rature, and other physical conditions under which it is formed. 



Bulimi being of less fugitive habits than most tribes of animals, 

 are distributed over the equatorial, tropical, and warm temperate 

 regions of the earth in assemblages of species limited in their range, 

 and, so far as regards the shell, of very distinct typical character. 

 The soft parts are much less variable, and being naturally sluggish, 

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

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

 Owing to their arboreal habits the author considers the Bulimi fitter 

 subjects for investigating the laws of geographical distribution than 

 the Helices which live more in the earth, and are less influenced by 

 the conditions with which they are surrounded. The few Bulimi 

 of ground habits differ typically but little in countries very remote 

 from each other. The localities of about five hundred species are 

 known, and the majority are registered M ith their circumstances of 

 habitation. Their area of geographical distribution lies between 40° 

 south and 35° north in the New World, and between 42° south and 

 60° north in the Old World ; that is, between the southern extremity 

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

 and Sweden in the latter; and there is no country within this area 

 of which the Bulimi do not form part of the zoology. Regarding 

 the shell with reference to its distinctions of form, composition, and 

 system of colours, for the little variation in the living animal seems 

 inadequate to the purpose, the Bulimi are distributed over this area 

 in seven provinces of about forty typical assemblages of species, of 

 which three-fifths inhabit the western hemisphere, and the remaining 

 two-fifths, with a wider range and greater local variety of character 

 in conformity with the more varied arrangement of the land, inhabit 

 the eastern. 



The author distinguishes the typical provinces of distribution as 

 Venezuelan, Brazilian, Chilian, Bolivian, Caucasian, Malayan and 

 African, and passes through the consideration of each in detail. 

 The conditions most favourable to the calcifying functions of the 

 Bulimi are an abundance of decaying vegetable matter, with an 

 equable temperature of from 80° to 85°, in dark, close, humid w^oods, 

 among shady thickets or in ravines. Near the sea-level in thin cal- 

 careous soil, and in sandy plains, where the vegetation is scanty and 

 parched, or in grassy savannahs, the shell is light and often vividly 

 coloured. In species which burrow in the earth, the shell is mostly 

 colourless, and often of glassy tenuity. 



The highest condition of the genus is in intertropical America, 



