HELIX. 



263 



Genus BULIMUS, Auct. 



generic characters. 



Animal. External fol•m■^^and characters correspond- 

 ing, in all respects, to those of Helix, variously modified 

 as to the proportion of the several parts, in different spe- 

 cies. Its peculiarities consist in its internal organization, 

 especially the genital apparatus. 



Shell. Form ovate, oblong, or turreted ; structure 

 sometimes thin and delicate, but generally thick and 

 solid ; surface smooth, very rarely folded or sculptured ; 

 color sometimes corneous, but generally more or less 

 variegated ; epidermis in some species extremely delicate, 

 in others very thick and firm, and having an independent 

 coloration. Aperture longitudinal, entire, ovate, simple, 

 or dentate ; lip disjoined above, either acute or reflected ; 

 columella straight, smooth, in a few species folded, never 

 truncated at base. Operculum none. 



Geographical Distribution. The Bdimi belong 

 to the tropics and the immediate vicinity ; and, though 

 not strictly limited to that region, are seldom found else- 

 where. Throughout this zone, they are found in every 

 part of the -(vorld in some of their forms ; though a par- 

 ticular form may prevail more exclusively in particular 

 countries. Tropical America and the Philippine Islands, 

 however, may be regarded as their favorite residences ; 

 while Africa and tropical Asia present us with but few 



