XVlll ANATOMY OP ACHATINID./E. 



aa. Apex of the globose type (figs. 1-5). 



fc. Columella conspicuously and abruptly truncated be- 

 low, Achatinoid; shell imperf orate. 



c. Apex involute at tip; whorls flattened, numer- 

 ous (12), the last whorl acutely earinated. 



Genus CERAS, p. 155. 



cc. Apex rounded ; shell slender, the post-embryonic 

 whorls smoothish (figs. 1-5). 



Genus HOMORUS, p. 130. 



ccc. Apex rounded, vertically ribbed or reticulate; 

 post-embryonic whorls rib-striate, the base 

 smoother; shell ovate-pyramidal or turrited 

 (figs. 6, 9). Genus PSEUDOGLESSULA, p. 156. 

 hb. Columella obliquely truncated at base; spire entire. 

 c. Turrite, composed of 10-15 compactly-coiled 

 whorls, pale, not variegated, vertically striate 

 and rarely 'hirsute; lip simple; columella trun- 

 cate or continuous. Sokotra. 



Genus RIEBECKIA, p. 204. 



cc. Ovate or oblong, composed of 6% to 9 whorls, 

 smooth or roughly sculptured, variegated; lip 

 simple or thickened; columella obliquely trun- 

 cate at the base. St. Helena. 



Genus CHILONOPSIS, p. 171. 

 Wb. Columella continuous below with the basal lip. 



c. Adult shell cylindric, truncated by the loss of 

 the early whorls, 4 to 7 whorls remaining. 



Genus RUMINA, p. 211. 



cc. Adult shell entire ; rimate or imperf orate ; large 

 (50-150 mm. long), with 7 to 10 whorls, oblong 

 or turrited, smoothish, covered with a yellow, 

 'brown-streaked cuticle. Madagascar. 



Genus CLAVATOR, p. 192. 



ccc. Shell entire, turrited, of 10-15 compactly-coiled 

 whorls; pale and smoothish, not variegated; lip 

 simple; columella truncated or continuous. 

 Socotra. Genus RIEBECKIA, p. 204. 



