MANUAL OF NATURAL HISTORY. 143 



out eyes or tentacles ; gills none external ; 

 body elongated, furnished with fins or swim- 

 ming lobes ; shell and operculum none. 



3. Family. — Pterosomes (Pterosomatidae). Body 



gelatinous, transparent, sub-cylindrical, with 

 a large thin horizontal wing-like fin on 

 each side ; eyes sessile ; tentacles none ; shell 

 none. 



4. Family. — Atalants (Atlantidae). Head with 



subulate tentacles ; eyes sessile on sides of 

 head ; body spiral, enclosed in a shell ; foot 

 with the front part in form of a vertical fin ; 

 hind part narrow, horizontal, operculigerous ; 

 shell spiral, transparent, carinated. 



TV. S UB-CLASS. — Pulmoniferous-Gasteropods 

 (Pulmonifera). 



Breathing organ in form of an air-sac or dorsal 

 cavity lined by a vascular net-work ; mouth with 

 transverse jaws ; respiring free air ; phytophagous ; 

 larva without cephalic fins. 



I. ORDER. — Adelopneumons (Adelopneumona). 



Edge of mantle united to nape, covering pul- 

 monary cavity except at a lateral aperture ; herma- 

 phrodite ; operculum none. 



L S UB-ORDER. — Terrestrial-Pulmonifers 

 (Geophila). 

 Eyes at apex of elongated cylindrical peduncles ; 



