CHAP. VI. ANALOGIES OP THE ACHATINA. 1?5 



families., before the whole tribe has undergone a careful 

 examination. 



(163.) The foregoing series, constituting the sec- 

 tional types of our sub-genus Achatina, will be ren- 

 dered more plain to the general reader, if thrown into 

 a table in the following manner : 



Analogies of the Species in the Sub-genus ACHATINA. 



Sectional Sub-genera Genera 



Division of Analogical Characters. of of the 



the Species, ACHATINA. ACHATIN*. 



C Ovate ; ventricose ; spire T 

 A. Zebra. < short; outer lip simple, > Achatina. ACHATINA. 



C not sinuated. j 



r Ovate; aperture nearly or} 

 A. elongata. < quite entire; spire more V Cochlicopa. BUIIMUS. 



C lengthened. 3 



A. P er V ersa. 



A. Sultana. '^ * j ^ostoma , HEUC,N A . 



A.virginea. { ^^^T^ * ' ^ ^hatinella. C^CLOSTOMA. 



Now, this is the smallest group which can be made 

 out, next to the actual species which come under each 

 section ; and yet every conchologist who possesses an 

 extensive series of these shells, or even of those we have 

 named, must perceive that no other divisions, or sec- 

 tions, can be formed with any degree of propriety ; that 

 is to say, if he were asked to single out the most diver- 

 sified forms from the sub-genus Achatina, the above are 

 those he would probably fix upon. Now, this series, 

 small as it is, turns out to have a circular succession ; 

 and not only that, but likewise to represent all the 

 sub-genera and genera of the family. Hence it would 

 seem that the essential character of this sub-genus is to 

 have the contour of the aperture simple not sinuated 

 or dilated, as in the next sub-genus, Cochlicopa. The 

 Cochlicopa maculata thus seems to be neither an Achatina, 

 nor a distinct sub-genus, as some have imagined, for we 

 do not believe it is a marine mollusk. 



(164.) The preceding analysis of Achatina inci- 



