AKIONID^. 
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. 
Fam. 1. ARIONID-zE. 
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. Aeion Ferus. (Land Soles.) 
Body elongate, lanceolate, united its whole length 
to the foot ; back keeled, attenuated behind ; 
* Ehrenberg proposes to call tbe tentacles of snails tenta- 
cular and those of pond snails, which do not bear eyes, 
vibracula. 
