ARCHACHATINA. 105 



veloped in a very large egg-capsule, of which but few are 

 brought forth at a time. Moreover, the embryonic whorls, 

 except the first, are sculptured. In Achatina the protoconch 

 is small, trochoidal and smooth. Archachatina differs from 

 Cochlitoma in the far more ample protoconch, and oviparous 

 reproduction. Archachatina has a shell of fewer whorls 

 than either of the other genera, in individuals of the same size. 

 In many of the more accelerated species of Archachatina the 

 decussate sculpture gives place on the last whorl to a smooth- 

 ish surface ; and the zigzag pattern of coloration may also be 

 condensed upon the spire, the later portion having a second- 

 arily simplified pattern. 



Archachatina was proposed by Albers for the typical sub- 

 genus of Achatina, as that genus was then understood in a 

 wide sense, that is, embracing Pseudachatina, Perideris, Gles- 

 sula, Stenogyroid groups, etc. ; this typical subgenus includ- 

 ing the. forms subsequently and up to the present time com- 

 prised in the restricted group Achatina. Ten years later the 

 group was reduced to a synonym of Achatina by von Martens, 

 a natural and proper course under the conditions then exist- 

 ing, for Albers' group covered species of all the groups now 

 to be recognized in the dismemberment of the genus Achatina. 

 In the meantime Herrmannsen in his classic work on mollus- 

 can genera (1852), had given Albers' first species, A. sinis- 

 trorsa (= bicarinata) , as an example or type of Archachatina. 



Under these circumstances it seems proper to restrict 

 Archachatina to species having the essential structure of 

 A. bicarinata, even though no such limitation was intended 

 by Albers, or indicated by any subsequent author. 



A. bicarinata, according to Rang, lays large oblong citron- 

 yellow eggs, varying in size from 14 x 20 to 19 x 27 mm. 

 The egg-shell is about .3 mm. thick. From three to five or 

 even six are found in the oviduct at one time. A. purpurea 

 also has large yellow eggs, the uterus containing four or 

 five at once. 



Key to Species of Archachatina. 

 I. Shell, sinistral, rough, 120-150 mm. long, bicarinata no. 1. 



