98 LIMN^ID^. 



orbis turritus. But the Linnean epithets ^'^spira pro- 

 minente ^' and '' spira obsoleta " appear unmistakeably 

 to distinguish the two species; and, at all events, it 

 would now be very inconvenient to make any change of 

 name by adopting that given by Miiller, instead of the 

 one by which this species is so universally known. The 

 late Dr. Fleming proposed to separate it generically from 

 the next under the name of Aplexa -, but this separation 

 has only been adopted by a very few conchologists. A 

 well-known European species, P. acuta, seems to con- 

 nect the two British forms, both as regards the soft parts 

 of the animal and the shell. 



B. MantU having lobes or digitated processes which expand 

 over the shell ; the latter being destitute of an epidermis 

 and having a short spire. 



2. P. fontina'lis"^, Linne. 



Bulla fontinalis, Linn. Syst. Nat. ed. xii. p. 1185. P. fontinalis, F. & H. 

 iv. p. 140, pi. cxxii. f. 8, 9. 



Body lustrous, dark grey with sometimes a sHght tint of 

 yellow or violet : mantle fringed with about a dozen lobes or 

 digitations of imequal size : tentacles rather slender, hght grey : 

 eyes conspicuous: foot obtusely rounded in front, and con- 

 tracted behind to a somewhat fine point. 



Shell oval, extremely thin, glossy, semitransparentjgrej-ish- 

 horncolour with a slight tinge of yellow or brown, faintly 

 striate by the Hues of growth and microscopically striate in a 

 spiral direction : vjhorJs 4-5, swollen, the last occupying con- 

 siderably more than three-fourths of the shell : spire not much 

 produced, blunt at its point : suture moderately deep : 7nouth 

 nearly of the same form as that of the preceding species, but 

 much larger and wider in proportion : o^lfer lip very thin and 

 flexuous : i7i7ier lip much spread on the columella, which has a 

 slight and narrow fold on its lower side. L. 0-35. B. 0-25. 



Yar. 1. injiata. Shell half as large again as the usual size : 



* Frequenting fountains. 



