LAND AND FRESH-WATER SHELLS 



OF 



NOETH AMEEICA. 



I. 



Order PULMONATA. 



LiXGUAL membrane short and broad; teeth numerous, 

 uniform, in numerous transverse rows. Mouth usually with 

 horny jaws. Eespiratory organ in the form of a closed 

 chamber lined with pulmonic vessels on the back of the 

 animal and covered by the shell; edge of the mantle 

 attached— the entrance to the air-chamber being through 

 an opening in the side, closed by a valve. Operculu'm 

 almost universally absent. Animal hermaphrodite, with 

 reciprocal impregnation, generally oviparous, terrestrial, 

 fluviatile or marine, but respiring free air. Tentacles and 

 eye-peduncles retractile or contractile. 



Shell varied in form, sometimes rudimentary or wanting. 



Eyes at the end of elongated peduncles, or on the he°ad 

 of the animal. 



The Pulmonata are usually divided into three suborders 



Geophila, Limnophila,^ and Thalassophila'' — names derived re- 

 spectively from the terrestrial, fluviatile, and marine habits of the 

 animals. 



Suborder GEOPHILA. 



Eyes at the tips of elongated, cylindrical peduncles ; tentacles 

 retractile or contractile, cylindrical, shorter than, and placed 

 under, the eye-peduncles, sometimes very small or wanting. 



' See Land and Fresli-water Shells, II, p. 1. 2 lb. p. 152. 



1 June, 1868. / 1 \ 



