CHAP. VI. 



ANALOGIES OF THE ACHATINiE. 



175 



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 

 Division of 

 the Species, 



A. Zebra. 



A. elongata. 



A. perversa. 

 A. Sultana. 

 A. virginea. 



Analogical Characters. 



Sub-genera Genera 

 of of the 



Achatina. Achatina. 



'X 



dchatina. Achatina. 



BULIMUS. 



r Ovate; ventricose; spire 



< short ; outer lip simple 

 L not binuated. 



rOvale; aperture nearly or 



< quite entire; spire more ^Cochlicopa 

 t lengthened. j 



f Spire lengthened and attenu- } ^acrn-imra 

 \ ated; body. whorl short. ^ ^^^acrospira. 



f Spire rather depressed; base > r v s tt„ 



\ deeply notched. jie«co5^ow«.? Helicina. 



C Aperture nearly round; lip ^ < 7 ,. „ ^ 



I margined. j ^chatmella. C\clostoma. 



Clausilia. 



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- 



