PLANORBIS. 39 



side. It lays from three to six eggs, and the fry are 

 hatched in about ten or twelve days afterwards. 



Var, cristata. — Shell smaller, ridges more distant, stronger, 

 and more distinctly crested. Not unfrequently found with the 

 typical form. 



4. P. al'bus,* Muller. Pl. IV. 



Body dirty brown, with a reddish tinge, indistinctly spotted 

 with black ; head large ; tentacles slender, pointed at their 

 tips, widely diverging at their base, rather transparent, light 

 yellow with a reddish tint ; eyes very small, nearly oval, black ; 

 foot dark reddish-brown, rounded in front, narrowing behind, 

 and ending in an obtusely pointed tail. 



Shell flattish above, with a hollow in the middle, more concave 

 below, thin, brittle, of a dull appearance, pale grey, closely and 

 delicately striate in the line of growth, more distinctly marked 

 with raised striae spirally ; epidermis thick, often clothed with 

 fine bristles, which are easily rubbed off; periphery somewhat 

 compressed, not keeled ; whorls 5, body whorl larger than the 

 rest ; suture deepish ; mouth roundish-oval ; outer lip somewhat 

 reflected ; inner lip spread on the base of the penultimate whorl, 

 and continuous with the outer lip ; umbilicus large. 



Inhabits lakes, ponds, and stagnant water in many 

 parts of Great Britain, as far north as Aberdeenshire. 

 It is a sluggish and irritable species, and carries its 

 shell on one side as it moves along. The eggs, which 

 number from four to ten, are enclosed in transparent 

 capsules of a roundish form, and the fry are hatched 

 in about twelve days. 



Var. Draparnaldi. — Shell with closer and sharper stride in the 

 line of growth ; periphery distinctly keeled ; timbilicus deeper. 

 Holbrook, Suffolk (Sheppard), Cardiff, Bristol, Church Stretton 

 in Shropshire (J. G. J.), B.C. Pond at Sandal near Wakefield 

 (Sheppard), near Birmingham (G. Sherriff Tye), J.C, 



♦ White. 



