HARr.REAVES : MOLLUSr.A IN THE SCARBOROUGH DISTRICT. 307 



borough Mere, Carnelian Bay, cliffs south of Spa, Cayton, East 

 Ayton, Castle Moat, West Ayton, River Derwent. 

 van laevigata Adami. — Scarborough Mere. 



Planorbis carinatus MUller. — Formerly abundant in Scar- 

 borough Mere; still occurs on the Carrs at Folkton, Flivton, and 

 Seamer. 



var. disciformis Jeffreys. — Scarborough Mere. 



Planorbis umbilicatus Miiller. — Not uncommon on the Carrs 

 from Folkton to Seamer. 



Planorbis vortex (Linne). — Known only from Scalby Cut near 

 Wyngate. 



Planorbis spirorbis (Linne). — Very abundant in ponds and 

 ditches north and south of Scarborough and on the Carrs ; Throxenby 

 Mere. Some years ago a small pond in Cayton Bay yielded hundreds 

 of scalariform monstrosities, but diligent search has failed to find any 

 in subsequent j^ears. 



Planorbis contortus (Linne). — Abundant where it occurs. In 

 ditches at Wyngate, throughout the Carrs, Snainton brickponds, Der- 

 went at Ayton. 



Planorbis fontanus (Lightfoot). — Ponds near railway between 

 Cayton and Lebberston, rare. 



Physa fontinalis (Linne). — Ditches on Folkton and Seamer 

 Carrs, River Hertford, Derwent from Ayton to Yedingham. Very 

 fine specimens have been obtained from near Folkton, the animal 

 being darker than the ordinary form. 



Aplecta hypnorum (Linne). — Abundant in ditches near Flixton, 

 Folkton, Seamer, and East Ayton ; Throxenby Mere. 



Bithynia tentaculata (Linne). — Formerly in Scarborough Mere 

 and ditches near. Abundant on Carrs from Cayton to Folkton and 

 Seamer, millrace at Scalby, Snainton brickponds. 



Vivipara contecta (Millet). — Specimens were introduced from 

 Askern into a pond in Cayton Bay in Nov., 1903, and have con- 

 siderably increased in numbers. 



Valvata piscinalis (Miiller). — Common in the Derwent from 

 Ayton to Sherburn, rare in ditches at Folkton, Flixton, and Sherburn; 

 River Hertford. 



Valvata cristata Miiller. — Ditch near Seamer, pond on Carrs, 

 Derwent at Ayton. 



Pomatias elegans (Miiller). — Formerly on Oliver's Mount, 

 Forge Valley on both sides of the river, 



