209 



It will be seen on reference to Plate //. that the animal of Achatina is 

 similar in all respects to that of Bidimus. M. Deshayes says, such is the 

 resemblance, that for him Achatina is an artificial genus. The generic 

 characters of the shells run also successively into one another, but they are 

 divisible into more distinctly typical groups. The animals oiBulimus oblongus 

 and Achatina regina are very like, but the shells of these two species are 

 essentially different. One is characterized by a massive, callous columella, 

 and thickened, reflected lip; whilst in the other the lip is not reflected, and 

 the columella is thinly rolled over, and truncated at the end. And so many 

 species partake respectively of these particular characters, in connection 

 with others, extending even to features of geographical distribution, that 

 the shell in this instance is a more important aid to classification than the 

 animal ; or, to speak correctly, there are better distinguishing characteris- 

 tics in the hard parts of the animal, than in the soft. 



The Achatina are not of the same arboreal habits as the Bulimi, but 

 dwell in places where there is more moisture, in swamps or in the vicinity 

 of lakes and rivers. They are divided by Pfeiffer into five sections, the 

 first, Achatina proper, being by far the most numerous, including the fine 

 series represented by the large A. variegata, zebra, and others, which are pecu- 

 liar to West Africa, and take the place of the Bulimi in that district. 



Another subgenus is that named Sjoiraxis, in which the shell is small, and 

 of a highly polished, horny texture. It includes many extremely beautiful 

 and delicate forms, chiefly inhabitants of the Central American continent and 

 archipelago. A group of still smaller species, distinguished by the subge- 

 neric name of Tornatellina, have the columella twisted ; and there remain 

 two other very distinct types, one represented by the well-known British 

 Azeca tridens, and the other by the large and singularly long-convoluted 

 shell, A. columna (Columna jiammeaj . 



1. accincta, Miglt. 



2. acicula, Mull. 



3. aciculoides, Jan. 



4. acuminata, Pfr. 



5. acuta, Lam. 



6. alabastra, Rang. 



7. albicans, Pfr. 



8. algira, Brag. 



9. allica, Reeve. 



10. amentum, id. 



11. angiostoma, Ad. 



12. Antoniana, Pfr. 



Species. 



13. aperta, Guild. 



14. arcuata, Pfr. 



15. assinrilis, Reeve. 



16. attenuata, Pfr. 



17. auvata, Mor. 



18. Azorica, Alb. 



19. bacilliformis, Jonas. 



20. balanus, Bens. 



21. balteata, Reeve. 



22. Bensouiana, Pfr. 



23. bicolor, Jay. 



24. Blainiana, Poey. 



25. Blandiana, Ad. 



26. bullata, Gould. 



27. Californica, Pfr. 



28. Candida, Shutt. 



29. carinata, Pfr. 



30. Canninensis, Mor. 



31. carnea, Pfr. 



32. Cassiaca, Bens. 



33. cerea, Pfr. 



34. Ceylanica, id. 



35. clavata, Gray. 



36. clavus, Pfr. 



2 E 



