AURICULACEA. 153 



More recent investigations have shown that they respire 

 free air, and that they are amphibious rather than aquatic. 

 Tlie systematic arrangement of this family may be seen 

 in the following tables, as proposed by Dr. Pfeiffer and 

 H. and A. Adams. The arrangement adopted in the fol- 

 lowing pages corresponds with that of the former. I do 

 not propose to refer to the many systems of other foreign 

 authors, but shall notice those proposed by Americans. 



By this table it will appear that Pfeiffer divides the air- 

 breathing MoUusks in two grand divisions; A, including 

 those furnished with four tentacles, and B, including those 

 with two only. The latter are also subdivided into «, 

 those not operculated, and b, those furnished with an oper- 

 culum. In the former of these subdivisions, he places the 

 family Auriculacea. 



In the " Genera of Recent Mollusca," the air-breathing 

 Gasteropods are divided into Inoperculate and Operculate. 

 The former are subdivided, according to their terrestrial, 

 lacustrine, and marine habits, into Geophila, Limnophila, 

 and Thassilophila. The second subdivision is composed 

 of the Auriculacea, under the name of ElobiadcB, and the 

 LimncBidce. 



In both of these systems, the family is placed nearest 

 to the fresh-water Pulmonates, with which they are more 

 closely allied than with the land snails. 



Dr. Pfeiffer (Mon. Auric. Viv.) thus divides the 



PULMONATA. 



C ^ I. Onchidiacea. 



A. Tetracera, \ < II. Limacea. 



[ { III. Helicea, 



{ I IV. Limnajacea. 



a. Inoperculata, 1 ^' Auriculacea. 



VI. Proserpinacea. 



{ I 



I 



,, j^. J f ( VII. Aciculacea. 



li. Liicera, ^ , ^ Xerrestria, . . I Vllf. Cyclostomacea. 



b. Operculata, \ ( IX. Helicinacea. 



T , ..,. (X. Aniphibolacea. 



(3. Aquatllia, . . ,., Amnnllnria^ftn. 



XI. Ampullariacea. 



20 



