PHYSA. 97 



transparent, yellowish or reddisli-horncolour, faintly striate by 

 the lines of growth, and marked spirally with a few very in- 

 distinct striae, which are only perceptible by means of a high 

 magnifying power : epidermis very thin : ivhorls 6-7, convex, 

 but slightly compressed at the sides, the last exceeding in size 

 all the rest put together : spire tapering, but blunt at its ex- 

 tremity : suture distinct, though not deep : movjJi oval, con- 

 tracted on the inner side by the periphery of the penultimate 

 wborl, acutely angulated above and rounded below: outer Up 

 thin and fiexuous : inner lip spread on the columella, which 

 has a strong and broad fold on its lower side. L. 0'5. B. 0-2. 



Habitat : Ponds, ditches, and among grass in pools 

 which are quite dried up in summer, throughout these 

 isles from the Moray Firth district to Guernsey; but 

 it is rather local. It is also an upper tertiary fossil. 

 A variety occurs in which the shell is smaller and of a 

 dark copper-colour; and I also possess a specimen in 

 which the spire is eroded and truncate, the opening 

 having been filled up by a shelly plate. Miiller recorded 

 a specimen which had only the right eye, the other being 

 wanting. It is a native of Siberia, and ranges southward 

 to Nice and the Eastern Pyrenees. According to Gould 

 and Philippi, it is the same species as the P. elongata of 

 Say, which inhabits the northern and western parts of 

 the United States. 



This mollusk is rather active in its habits, and may be 

 seen in fine weather floating with tolerable rapidity. It 

 is rather prolific ; and the young attain their full size at 

 the end of the second year. The largest specimens I 

 have ever seen of this species were found by me more 

 than a quarter of a century ago, in fish-ponds at Fre- 

 mington, in the north of Devon, some of which are 

 three-quarters of an inch in length. 



Gmelin supposed that the Bulla hypnorum of Linne 

 might be a variety of the next species ; and Miiller, for 

 nearly the same reasons, called the present species Plaii- 



F 



