96 THE LAND AXD FRESHWATER MOLLUSCA OF DORSETSHIRE. 



Genus IY.ANCTLUS, Geoffrey. 



This genus was for some time considered as a Patella in minia- 

 ture, and that it was branch) t'erous instead of pulmoniferous, as it 

 is now ascertained to be. In 1828 Mr. Gwyn Jeffreys relegated it 

 to the Litnnaeidae, and Moquin Tandon proved it to be amphibious. 

 The point ot the spire turns to the rinht or left, according to the 

 species, it is rudimentary, indicating the direction of the volutions. 

 There are three European species, two of which are found in 

 Britain, the other seems to be confined to Corsica. 



1. ANCYLUS FLUVIATILIS, MulUr, pi. 7. 



PATELLA LACUSTRIS, Pult. cat., p. 51. Rack, ed., p. 58, pi. 

 22, f. 8. Brit. Conch., vol. 1, p. 120. 



Body slate colour or dark grey with green-black specks. 



Shell semi-oval, formed in the shape of an ancient helmet, with fine, 

 regular, radiating, longitudinal striae, which are often met trans- 

 versely by others equally fine,ratherthin, fragile, not glossy, yellow- 

 ish grey or horn-colour; anterior margin rather the narrowest; 

 spire acutely peaked and hooked, the slope forward being much 

 arcuated ; spire rather blunt and turned a little to the right ; mouth 

 oval. L.0.2, B.0.233. 



Var. 1 Capuloides. Shell larger and higher, with the beak 

 not placed so near the posterior margin. L.0.415. B.0.3, 



Var %gibbosus. Shell smaller, more swollen, with the beak 

 reaching: or overhanging the posterior margin. A. gibbosus, Bour- 

 guiernat in Journ. de Conch, iii. (1853;, p. 186. 



Var. 3. albidus. Shell milk-white and more finely striated. 



Hab. On stones and rocks in shallow rivers and streams. 

 River Stour, Spettisbury ; river, Chamberlayne's, Bere Regis -, 

 Godlingston, near Swanage (J.C.M.P). Var. I. River, 

 Corfe, very rare (Gwyn Jeffreys). Var. 2. Osmington 

 Mills, near Ringstead (Gwyn Jeffreys). Var 3. Arish Mill, 

 near Lul worth (Gwyn Jeffreys). 



2. A. LACUSTRIS Linn. pi. 7. 



ANCYLUS OBLONGUS, F. and H., p. 188, pi. cxxii., f. 5. 



PATELLA OBLOXGA, Pult. cat., p. 51, Rack, ed., p. 58, pi. 18, 

 f. 20, and pi. 22, f. 8 a. 



PATELLA LACUSTRIS, Mont, (not Linn.). Test. JBrit., vol. ii., 



p. 484. 



Shell oblong, more or less depressed, obliquely twisted to the left, 

 smooth and thin, with very fine undulating longitudinal striae 

 which are met by other transverse ones equally indistinct or more 



