80 TERRESTRIAL AIR-BREATHINQ MOLLUSKS. 



Succinea Wilsoni, Lea. Succinea obliqua, Say. 



Concordialis, Gld. Totteniana, Lea. 



luteola, Gld. campestris, Say. 



lineata, W. G. Binn. Hawkinsi, Bd. 



avara, Say. rusticana, Gld. 



Stretchiana, Bid. Nuttalliana, Lea. 



Verrilli, Bid. Oregonensis, Lea. 



aurea, Lea. effusa, Shuttl. 



Groenlandica, Beck. Salleana, Pfr 



VTI. DESCRIPTIONS OF GENERA AND SPECIES. 

 Order PULMONATA. 



Lingual membrane varying from short and broad to long and 

 narrow ; teeth numerous, in numerous uniform transverse rows. 

 Mouth usually with one or more horny jaws. Respiratory organ 

 in the form of a closed chamber lined with pulmonic vessels on 

 the back of the animal and covered by the shell when present ; 

 edge of the mantle attached, — the entrance to the air-chamber 

 being through an opening in the side, closed by a valve. Oper- 

 culum almost universally absent. Animal hermaphrodite, with 

 reciprocal impregnation, generally oviparous, terrestrial, fiuviatile 

 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 head of the 

 animal. 



The Pulmonata are usually' divided into three suborders, — Geophila, 

 Limnophila, and Thalassoj^hila, — names derived respectively from the 

 comparatively terrestrial, fiuviatile, and marine habits of the animals. 

 These suborders are readily distinguished by the position of the eyes, 

 either sessile or on peduncles, and the characters of the tentacles. 



I have included in this volume only the species of the first suborder, 

 though one species of the Limnophila, Carychium exiguum, is truly 

 terrestrial. It will be understood also that I do not include any gill- 

 bearing genus, however terrestrial may be its habits. Thus I omit 

 mauy genera included in Vols. II. and IV. 



