118 



the latter named shell was, before the publication of 

 the splendid work " The British Mollusca," considered 

 as a distinct species, but is now described as a variety 

 only, under the appellation of var. gracilis. 



Having carefully examined these shells for some 

 time, it is with some hesitation that I adopt Professor 

 Forbes's combination, for the animal is so very diflFerent 

 in size, colour, and habits. The animal of Succinea 

 putris is pale flesh-coloured, while that of Succinea 

 Pfeift'eri is a leaden-black ; the former is double the size 

 of the latter. The Succinea putris is chiefly found on 

 the stems and leaves of water and bog plants, wbils' 

 the Succinea Pfeifferi is found on the mud at the edges 

 of streams. It is not difficult to collect specimens of 

 both these shells varying in such a manner that a 

 gradual series may be obtained connecting the two 

 species, but the same may be done with other species, 

 such as the Pisidiums, and especially connecting in a 

 gradual series Planorbis carinatus with Planorbis mar- 

 , ginatus, Planorbis nitidus with Planorbis lacustris. 

 Helix refescens with Helix hispida, Helix caperata 

 with Helix virgata, Paludina Listerii with Paludina 

 vivipara, Limnaeus pereger with Limnseus auricularius, 

 and Valvatacristata with Valvata piscinalis, yet all con- 

 chologists agree in pronouncing each a distinct species. 

 It is, therefore, probable that Succinea putris may yet 

 again be separated from the now so-called var. gracilis. 



The form varies considerably, it is generally some- 

 what conical, nearly transparent, shining, very fragile, 

 thin, smooth, and pale amber-coloured. The body 

 whorl very large. There are three or three and a half 

 convolutions. 



The length is sometimes three-fourths of an inch. 



First described by Dr. Lister, in the year 1678. 



Inhabits damp places, on succulent plants near water. 



