

ANCYLUS. 121 



Dorset : very rare (J. G. J.). Var. 2. Sark ; Osmington 

 mills, near Ringstead, Dorset ; Dunboy, near Bearhaven, 

 Co. Cork (J. G. J.). This last variety is the A. deper- 

 ditus of Ziegler and Dupuy; but (according to Bour- 

 guignat) not of Desmarest, who first used that name 

 for another species. Intermediate forms in respect of 

 the position of the beak incline me to consider this only 

 a variety. Var. 3. Wokey hole, near Wells (Beevor) ; 

 Scarborough (Bean) ; near Torquay (Norman) ; Arish 

 mill, near Lulworth, Dorset (J. G. J.). Specimens 

 from different places vary in colour from white to dark- 

 horncolour or reddish-brown. This species is also one 

 of our upper tertiary fossils. Abroad it ranges from 

 Finland to Algeria and Sicily ; and the Rev. R. T. Lowe 

 has included it in his list of Madeiran land-shells. 



M. Bouchard-Chan tereaux published, nearly thirty 

 years ago, an extremely interesting account of the em- 

 bryogeny of A. fluviatilis, illustrated by a plate showing 

 the successive development of the spawn into the fry. 

 He says, each individual lays, in the course of the breed- 

 ing-season, about 80 eggs, which are enclosed in from 

 7 to 10 capsules and arrive at maturity in from twenty- 

 four to twenty-seven days, according to the temperature. 

 The animal seems to be more fond of Fontinalis antipy- 

 retica than of any other plant. 



Many species have been carved out of this variable 

 kind by Continental authors. In very young shells may 

 be detected faint traces of a more complete spire, which 

 is intorted so as to cause a concavity in the beak, called 

 by M. Bourguignat the "depression apicale." This 

 species was first made known by Lister, and described 

 by him under the name of Patella fluviatilis, but ac- 

 companied by other epithets. It has by some authors 

 been considered to be the Patella lacustris of Linne* ; 



