176 FKESH-WATEE AQTJAKIA. 



The colour of tte animal is a kind of violet-brown, the lower 

 part of the body being of a lighter shade. The body itself 

 is slender and the head large. The sheU is thin and com- 

 pressed, not quite l^in. in diameter, a little ooncave above and 

 flat "below, so flattened indeed as to cause the periphery to 

 be prominently keeled at the lower side. The colour of the 

 shell is a glossy brown, and there are from six to eight 

 whorls. The aperture is slightly angular. This snail lays 

 about fourteen eggs, and incloses them in an orbicular 

 capsule. They are hatched in from ten to fourteen days. 



Planorbis spirorbis is smaller and thicker than the last 

 species : it is found in the sluggish or stagnant water of 

 almost every part of Britain. The animal is of a purplish- 

 grey ; the tentacles are long, thread-Uke, and pointed at the 

 tips ; the disc is spotted with black. The shell is glossy 

 brown and shghtly concave on both sides, or sometimes 

 rather flat below: it very much resembles that of P. vortex, 

 but it is less in diameter, rather thicker, and possesses fewer 

 whorls. The periphery is very slightly keeled below; the 

 aperture is almost round. This species also, when out of 

 water, closes the mouth of its shell with an epiphragm. 



Planorbis albus is a beautiful snail, found in the slow- 

 running and stagnant water of many parts of Britain. The 

 body of the animal is greyish, and faintly spotted with black ; 

 the head is rather large, and the tentacles are slender. The 

 shell, which is marked with raised spiral strise (thread-hke lines), 

 is thin, brittle, about jin. in diameter, and of a very light 

 horn-colour. The epidermis of the shell is thick, and is more 

 or less covered with fime bristles. There are five whorls, and 

 the sutures are rather deep. P. albus lays from ten to four- 

 teen eggs, and incloses them in an orbicular capsule. The 

 fry are hatched in from twelve to fourteen days. 



Planorbis lineatus is not a very common snail, and is found 

 only, as a rule, it is said, in the Home and Eastern Counties, 

 and occasionally in Yorkshire and Nottinghamshire. The 

 body of the animal is of a purplish-brown colour. The tentacles 

 are long, thread-Uke, and yeUowish-brown. The disc is small, 

 broad, and tapers to a point behind. The shell is usually 



