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 striae in the 

 line of growth ; periphery distinctly keeled ; umbilicus 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. 



