AND THEIR INHABITANTS. 225 



species of Planorbis, of which the largest and most 

 conspicuous is P. corneus. 



On the banks overhanging the river Ouse I found 



GREAT EQUISETUM. 



the Butter Burr (Petasites vulgaris) in flower, and the 



Great Equisetum (E. telmateia) ; the leaves of the 



former do not appear till summer. The most luxuriant 



Q 



