MA1AC0Z0A. GASTEROPODA.. PULMOBRANCHIATA. AQUATICA. 49- 



obtuse tentacula; foot oval, anteriorly bilobate. Shell 

 oval or oblong, thin, fragile, with a tapering pointed 

 spire, the aperture longer than wide, oval, thin-edged, 

 the columella with an oblique plait. Aifxvrj, a marsh or 

 pool. Draparnaud. 



1 . Limnceus pereger. — Shell ovate, thin, horny, with 

 the spire short, acute, the last turn very large, the 

 aperture ovate. Peregrinor, "to travel through strange 

 places." 



A. L. pereger ovdtus. Ovdtus, egg-shaped. 



B. L. pereger communis. Communis, common. 



C. L. pereger limosus. Limpsus, living in mud. 



2. Limnceus palustris. — Shell oblong, conical pointed, 

 with the spire rather elongated, the turns forming an 

 acute margin along the suture, the aperture ovato- 

 oblong. Palustris, residing in marshes. 



3. Limnceus truncatulus. — Shell ovato-oblong, coni- 

 cal, pointed, the turns somewhat abruptly curved at 

 their upper margin, the aperture ovate or ovato-oblong. 

 Named from the flattening or truncation of the turns. 



A. L. truncatulus oblongus. Oblongus, longer than broad. 



B. L. truncatulus fossdrius. Fossdrius, in ditches. 



C. L. truncatulus minutus. Minutus, very small. 



Genus 2. Physa. — Animal with two long, slender, 

 tapering tentacula, the mantle with two expansile digi- 

 tate lobes. Shell sinistrorse, oval, glossy, transparent, 

 the last turn very large, ovate, ventricose, the aper- 

 ture ovato-oblong, very narrow and acute behind. <&vo-aco, 

 to inflate or blow out. Draparnaud. 



1. Physa fontindlis. — Shell oval, transparent, glossy, 

 with the spire very short, the aperture ovato-oblong, 

 occupying about half the size of the inferior surface. 

 Fontindlis, residing in springs or streams. 



Genus 3. Planorbis. — Animal very slender, elongated, 

 involute, with two very long, setaceous tentacula. Shell 

 orbicular, flat, coiled nearly in the same plane. Planus, 

 flat ; drbis, ball. Muller. 



1. Plandrbis Vdrtex. — Shell orbicular, extremely de- 

 pressed, pellucid, slightly concave above and beneath, 



E 



