UNIVALVES. 
57 
throughout Great Britain. The shell is ovately 
conical, of a yellowish horn-colour, smooth and 
semi-transparent, very frequently incrusted with a 
green confervoid growth. There are five or six 
whorls, the last one large; aperture oval, angular 
behind, the shelly operculum closely fitting the 
aperture, no umbilicus. Shell half-inch long, 
three-tenths wide. The animal is blackish, 
speckled with golden-yellow dots; the foot is lobed 
in front, narrow and rounded behind; the ten¬ 
tacles long and slender; eyes black, large, and ses¬ 
sile. Bouchard says that Bithinias deposit their 
eggs on stones and aquatic plants; the female 
lays from thirty to seventy eggs in a band of three 
rows, cleaning the surface as she proceeds; the 
young are hatched in three or four weeks, and 
attain their full growth in the second year. 
Bithinxa Leachii (PI. III., fig. 13), named 
after Dr. Leach, one of the earliest systematic 
writers on English zoology. The shell of this 
species is much smaller than that of the last, 
being about a quarter of an inch long and two 
lines broad; the whorls are more swollen and 
rounded, distinctly separated by a deep suture; 
the aperture is nearly circular, and there is a 
small umbilicus. It is found in the same habitats 
as the last, but is local and less abundant, and 
is confined more to the southern and middle 
counties of England. 
