BYTHLVIA. 29 



ternally with a strongish white rib ; vnier lip joined to the base 

 of the penultimate whorl and forming with the outer hp a com- 

 plete peristome ; umbilical chink very narrow ; operciihim thick, 

 oval, angulated above, centre depressed, finely striated concen- 

 trically, and made up of a series of plates rising one above 

 another, which have been formed by the animal at difterent 

 stages of its growth. 



Inhabits slow-running streams, ponds, and ditches 

 in most parts of England, Wales, and Ireland ; in 

 Scotland, where it seems to be very local, it has 

 been observed in Aberdeenshire ; the Rev. J. McMur- 

 trie informs me that it occurs abundantly in the 

 canal at Edinburgh, and I have found it in Dumfries- 

 shire. 



It is an inactive and irritable mollusc ; w^hen 

 touched it instantly retreats into its shell. It fre- 

 quently floats on the under surface of the water, 

 and when crawling carries its snout turned upwards. 

 In winter the animal is said to assume " a yellowish 

 chestnut-colour" (Daniel), B.C.^ Supplement, vol. v. 

 p. 151. 



Var. I. ventricosa (Menke). — Shell white, whorls more tumid. 

 Devonshire, Bristol, Wandsworth, Richmond, Surrey, B.C. 

 Near Birmingham (G. Sherriff Tye), J.C. 



Var. 2. excavata. — Whorls rounder; suture deeper. Wool- 

 wich, Cardiff, Co. Armagh, B.C. Kirkthorpe, near Wakefield 

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



Var. 3. albida, — Shell white. Near Birmingham (G. Sherriff 

 Tye), J.C. Near Colchester (Laver). 



Monst. decollata. — Upper whorls wanting in half-grown and 

 adult specimens, their place being supplied by a nearly flat 

 seraispiral plate, as in Bulimus decollatus. Woolwich, Cardiff, 

 Co. Armagh, B.C. Near Birmingham (G. Sherriff Tye), near 

 Wakefield (J. Hebden), J.C. 



