Till ACHATINIDCE. 



stripes; wliorLs without internal lamellae and coiled 

 around a slender axis, which is solid or nearly so. 

 African. (See below.) 



II. Subfamily STENOGYREST^;: Shell turrited or cylindric, 

 unicolored or having darker streaks, rarely if ever zigzag- 

 striped. No internal lamella ; 'axis slender, solid or 

 nearly so. Tropical in both hemispheres (see p. xvi). 

 III. Subfamily COELIAXIN^E. Stenogyroid forms with inter- 

 nal lamella, the axis usually tubular. West and South 

 Africa, and Parisian Eocene (see vol. xviii). 



Subfamily ACHATININ^E. 



This group comprises about a dozen genera, which may be 

 arranged as follows, the general sequence being from the 

 more advanced to the less specialized groups, allied forms be- 

 ing bracketed together. 



Pseudachatina. Limicolaria. 



fColunma. ( AtopococUis. 



| Arehachatina, ] Pseudotrochm 



( Perideriopsis. 

 r Metachatina. 

 i Cochlitoma. 

 ( Achatina 

 (Burtoa 



The soft anatomy of the groups is noticed below. All the 

 forms examined conform closely to a common type, with three 

 exceptions. In Limicolaria vanattai and CochUtoma craw- 

 fordi I found the penis to have a true retractor, inserted dis- 

 tally on the diaphragm, while in 'all other forms known there 

 is a secondary retractor, a branch of the right ocular band, 

 and belonging to the columellar system, this structure being 

 regarded as characteristic of Achatinidce. The other notable 

 structural divergence is in the radula of Callistoplepa, which 

 has the middle tooth as wide as the laterals, its cusp well de- 

 veloped. In all other known Achatinidce it is much narrower, 

 with the cusp reduced. 



