179 



16. glaber, Midler. 



17. glutinosa, id. 



18. gracilis, Jay. 



19. humilis, Say. 



2 . intermedia, Terussac. 



21. involuta, Harvey. 



22. Lessoni, Deshayes. 



23. luteola, Lamarck. 



24. macrostoma, Say. 



25. marginata, Michaud. 



26. megastoma, Say. 



27. membranacea, Porro. 



28. minuta, Drapnd. 



29. Moravica, Parreys. 



30. ovalis, ©my. 



31. ovata, P/rapnd. 



32. palustris, z'a?. 



33. papyracea, jS^iar. 



34. peregra, Draparnaud. 



35. reflexa, #fly. 



36. rufescens, Gray. 



37. rugata, Ziegler. 



38. Sicula, Parreys. 



39. stagnalis, Draparnaud . 



40. strigata, Parreys. 



41. subglobosa, Sowerby. 



42. succinea, Deshayes. 



43. Tknorensis, Sowerby. 



44. trancatula, Midler. 



45. turrita, «/. 



46. umbrosa, /Say. 



47. Virgmiana, Lamarck. 



48. viridis, Q?foy. 



49. Ziegleri, Pfeiffer. 



Figure. 



Lymn^a stagnalis. PI. 17. Fig. 92. Shell, showing its light horny 

 substance and inflated growth. 



Genus 3. PHYSA, Draparnaud. 



Animal ; having a broad head, with the tentacles subidate or seta- 

 ceous, with the eyes placed at their inner bases ; foot lanceo- 

 late ; mantle lobed or simple. 



Shell ; oblong or ovate, mostly sinistral and polished ; sjnre 

 sharp ; aperture frequently oblong-triangular, lip simple. 



The animal of Phgsa varies from the typical form of that of Lymnaa, in 

 having the foot lanceolate and the tentacles more slender. The shell may 

 be best distinguished by its being mostly sinistral, and in having a polished 

 porcellanous surface. The species are of a darker horn-like colour, and 

 affect the same habitats. 



A British species, in which the mantle of the animal js not lobed, has 

 been made genus Aplexus, and a few in which there is an inclination in 

 the columella of the shell to be truncated, after the manner of Achatina, 

 have been separated under the generic title of Physopsis. 



Speaking of the Physa fontinalis, Professor Porbes says : — " The animal 

 is of a pale yellowish-grey, darkening in individuals to a deep-fuscous hue. 

 Its tentacles are long and slender, with conspicuous black eyes at their 

 inner basis. The mantle is highly contractile, and, when expanded, enve- 

 lopes a great part of the shell (indicated by its polished surface), and is 

 divided at the edge into finger-like processes. It is hi lobed, th ceolu- 



2 a 2 



