Dr. Tate on the Mollusca of Alnwick. 117 



pears to be peculiarly favourable to the development of land 

 shells, probably from the amount of inorganic salts it contains. 

 Besides the present mollusc, the following also live upon it : 

 Helix fusca, H. sericea, H. rotundata, Zonites alliarius and 

 nitidulus, Zua lubrica and Pupa umbilicata. 

 S. putris, var. gracilis. 

 In wet situations on a poor soil in exposed situations. 

 Alnwick moor, Dunstanburgh, and Alnmouth. 



Fam. Limn^ad^. 

 Gen. Physa, Drap. 



33. P. fontinalis, Linn. 



On aquatic plants in ponds and rivers, Howick pond, river 

 Aln. I kept several specimens of this shell in an aquarium 

 for some months. They can raise themselves in water and 

 sink at pleasure, as 1 have often observed, without having re- 

 course to plants or other aids to assist their progress. They 

 have, moreover, the power of walking along immediately 

 beneath the surface of the water. Their usual mode of pro- 

 gression is by a series of jerks. In ascending or descending 

 through water, the movement is a gradual and uninterrupted 

 one. 



Gen. Planorbts, Miill. 



34. P. albus, Miill. 

 Howick pond on aquatic plants. 



35. P. glaber, Jeff. 



Fosse at Dunstanburgh Castle, on aquatic plants. 



36. P. spinorbis, Linn. 



Fosse at Dunstanburgh castle and in the Kimmere lough, 

 on aquatic plants. 



Gen. Lymn^us, Drap. 



37. L. pereger, Miill. 



Common in ponds, ditches, and bogs. Alnwick moor, 

 Hulne woods, &c. 



L. pereger, var. ovatus. 

 In a small pond near Dunstanburgh Castle. 



38. L. truncatulus, Miill. 



Frequent in ditches and bogs. Alnwick moor, &c. 



Gen. Ancylus, Geoff. 



39. A. fluviatilis, Miill. 



Common on stones in running water. River Aln, Rugley 

 burn, &c. 



40. A. lacustris, Miill. 



Rare. In the Kimmeie lough upon the leaves of Nuphar 

 latea. 



