SWANTON : THE MOLLUSCA OF WILTSHIRE. 187 



Unio pictorum (Linne). — Apparently a local species. At the 

 present time it has been recorded only from the Kennet Canal and 

 its reservoirs at Devizes (Vize and Heginbothom). 



Unio tumidus Retzius. — Recorded from the northern part of the 

 county only; has not, as yet, been observed south of the Kennet Canal. 

 Canal at Devizes (Miss Cunnington and Vize); canal at Swindon 

 (Cockerell); canal at Wantage (Bromehead). 



var. ovalis Montagu. — "This very strong variety is not 

 uncommon in the Avon that runs through the north of Wiltshire and 

 Somersetshire, inhabiting the deeper parts of the river" (=Mya ovalis, 

 Test. Brit., pp. 34 and 563). From the Avon and Froome, Wiltshire 

 (Turton, as Mysca ovata). 



Anodonta cygnaea (Linne). — Widely distributed in the canal, 

 and occurs in all the largest ponds. Numerous in the canal at Trow- 

 bridge, canal at Devizes, the moat at Britford, Longleat (Vize); 

 canal at Wantage (Bromehead); canal at Devizes (Heginbothom); 

 Stourton ponds and Longleat (E.W.S.). 



var. incrassata Sheppard. — "This shell we found in great 

 abundance in the River Avon about Lackham" {=Mytilus avonensis. 

 Test. Brit., p. 172). "Miss Bennett, of Norton House, favoured me 

 lately with specimens from Tisbury, Wiltshire. They were old shells, 

 and the animal having lived in water highly impregnated with chalk 

 and calcareous matter, its epidermis has been secreted so rapidly and 

 increased the shell so much in thickness that the Linnean character 

 'testa fragilissima' is entirely lost" (Gray's Turton, p. 292). Specimens 

 from the Norton House garden pond, labelled "grown to this size by 

 good living," may be seen in the Cunnington collection at the Devizes 

 Museum. Mr. J. W. Taylor remarks: "A characteristic specimen of 

 this variety from a brook at Tisbury, Wiltshire, kindly given to me by 

 the late Mr. J. Pickering, weighs 2,227 grains or 5 "12 ounces, while 

 an example of the typical form of equivalent size from Nagden, near 

 Faversham, collected by the late Miss E. B. Fairbrass, weighed only 

 322 grains, or about one-seventh the weight of the variety incrassata" 

 (Mon. L. & F. W. Moll, i., 79). 



Sphaerium rivicola (Leach). — Locally abundant. "Frequently 

 to be found at certain seasons in the canal at Trowbridge, Milford, 

 near Salisbury, canal at Devize^" (Vize); Devizes (Miss Cunnington 

 and Heginbothom); Salisbury Avon (E.W.S.). 



Sphaerium corneum (Linne;. — A common species. Canal at 

 Trowbridge (Vize); Great Bedwyn (Townsend) ; Swindon (Cockerell); 

 Devizes (Miss Cunnington and Vize); ponds at Stourton, and Avon 

 at Salisbury (E.W.S.). 



Sphaerium lacustre (Miiller). — Widely distributed. Swindon 

 (Cockerell); Great Bedwyn (Townsend); Drew's Pond, Devizes (Miss 



