54 MOLLUSCA. TRACHELIPODA. 



Gen. 65. LYMN.EA, Lam. Helix, Lin. 

 Shell oblong, sometimes turreted, with projecting spire ; aperture 

 entire, longer than broad ; outer lip edged, the lower part ris- 

 ing on the pillar, and forming an oblique plait ; no operculum. 



L. stagnalis, Lam. Shell oblong, ventricose, pellucid, with the spire 

 produced and subulate j aperture large, ovate ; lip spreading ; co- 

 lour reddish gray or dusky. 2 inches long. Inhabits Europe in 

 ditches and ponds. B. Pen. Brit. Zool. iv. pi. 89, fig. 1. 



L. auricularia, Lam. Shell imperforate, ovate, thin, diaphanous, 

 of a horn colour, with a very short pointed spire, the aperture 

 much expanded, and the body whorl constituting almost the whole 

 shell, f inch long. Inhabits Europe in fresh waters Pen. Brit. 

 Zool. iv. pi. 89, fig. 4. 



L. peregra, Lam. Shell ovate oblong, thin, pellucid, longitudinally 

 striated, of a pale horn colour ; whorls convex, sutures hollow ; 

 spire acute. 7 lines long. Inhabits Europe in fresh waters. 

 Mont. Test. pi. 16, fig. 3. 



Gen. 66. PHYSA, Lam. Sulla, Lin. 



Shell convolute, oval or oblong, with projecting spire ; aper- 

 ture oblong, narrowed above ; pillar twisted ; right margin 

 very thin, edged, advancing in part above the plane of the 

 opening ; no operculum. 



This genus, established by Draparnaud, includes those fluviatile shells, in general 

 sinistral, which have been confounded with the Bullse, but from which they are 

 distinguished by their produced spire. The animal is furnished with two subulate 

 tentacula, with eyes at their internal base. 



P. Jbntinalisj Lam. Shell sinistral, oval, diaphanous, smooth, yel- 

 lowish horn colour ; spire short, acute. 6 lines long. Inhabits 

 ponds and rivers in Europe. Brown's Illust. pi. 41, fig. 54, 55. 



P. hypnorum, Lam. Shell sinistral, ovate, oblong, smooth, diapha- 

 nous, shining, yellowish ; spire exserted, slightly acute, spotted 

 with black. Inhabits rivulets, &c. on aquatic plants. Pet. Gaz. 

 pi. 10, fig. 8. 



Gen. 67. PLANORBIS, Lam. Helix, Lin. 

 Shell discoid, with the spire flattened, and the whorls apparent 

 on both sides ; aperture oblong, lunulate, the border not re- 

 flected ; no operculum. 



The spire in this genus is on a horizontal plane, with the inferior surface, however, 

 more flattened or concave. They are found in fresh waters, and the shell is gene- 

 rally thin, fragile, and diaphanous. The animal has the neck elongated, two subulate 

 tentacula, and the eyes at their internal base. The orifices for the anus and respi- 

 ration are on the left side. 



P. corneus, Lam. Shell opaque, chestnut or horn-coloured, with 

 four rounded striated whorls, separated by a deep suture; upper 

 side more concave than the lower. 1 inch in diameter. Inha- 

 bits Europe in stagnant waters Pen. Brit. Zool. iv. pi. 86, fig. 3. 



P. carinatus, Lam. Shell flat, concave above, and the whorls dc- 



