AKIONIDjE. 67 



genera or subgenera of Zonites, Helix, and Bulimus : 

 thus Helix elegans has the jaws of a Bulimus, Bu- 

 limus acutus of a Helix, and Helix candidissima of a 

 Zonites. M. Tandon proposed to move these species 

 to those genera for these reasons ; but, if his figures 

 of the jaws of the different kinds are examined, it 

 will be found that there are only a few of the ex- 

 ceptional species. 



Earn. 1. AEIONID^E. 



Head and tentacles retractile* into the skin, which 

 covers them as a sheath, being drawn into the 

 cavity of the body ; the end of their tail is as it 

 were truncated, and furnished with a transverse 

 lunate, or an erect longitudinal, gland on its 

 upper edge; the respiratory cavity is in the 

 front of the body, with the hole in the front 

 of the mantle's edge; and the orifice of the 

 generative organs is placed on the right side, 

 near, or immediately under, the respiratory 

 aperture (fig. 28.). The shell is presented in 

 very different degrees of development in the 

 different genera, it is very rudimentary in the 

 only English one. 



1. AKION Firm. (Land Soles.) 



Body elongate, lanceolate, united its whole length 

 to the foot ; back keeled, attenuated behind ; 



* Ehrenberg proposes to call the tentacles of snails tenter 

 cula, and those of pond snails, which do not bear eyes, 

 vibracula. 



F 2 



