138 CATALOGUE OF THE MOLLUSCA 
2. P. atsBus, Jill. 
Planorbis albus, Gray, Turt. Man. 259, t. 8, f. 97. 
In ponds and slow streams, frequent. 
3. P. pavis, Alder. 
Planorbis levis, Ald. in Newe. Nat. Hist. Tran. ii. 337. 
Gray, Turt. Man. 261, t. 12, f. 148. 
In ponds at Whitley Quarries, and on Holy Island. 
4. P. nautitEeus, Linn. 
Planorbis imbricatus, Gray, Turt. Man. 261, t. 8, f. 94. 
In ponds, frequent. 
5. P. carinatus, Mill. 
Planorbis carinatus, Gray, Turt. Man. 262, t. 8, £. 89. 
Rare. Near Stockton.—Mr. W. Backhouse. 
6. P. umpriicatus, Jill. 
Planorbis complanatus, Ald. in Newe. N. Hist. Trans. i. 31. 
Planorbis marginatus, Gray, Turt. Man. 265, t. 8, f. 87, 88. 
In ponds and ditches, not common. Prestwick Car, Ryton 
Haughs, and near Stockton. 
7. P. sprrorpis, Linn. 
Planorbis spirorbis, Gray, Turt. Man. 268, t. 8, f. 98. 
In ditches, common. 
8. P. nrtipus, Mull. 
Planorbis nitidus, Gray, Turt. Man. 268, t. 8, f. 93. 
Rather rare. In ponds at Redheugh. Benwell engine pond. 
—W. Sutton. Near Middleton-one-Row and Stockton.—J/. A. 
9. P. conrortus, Linn. 
Planorbis contortus, Gray, Turt. Man. 270, t. 8, f. 96. 
In ditches and ponds, not common. Prestwick Car, Gosforth 
Lake, Ryton Haughs, near Wooler, and near Stockton. 
41. ANCYLUS, Geoffroy. 
1. A. rLuvratiuis, Dill. 
Ancylus fluviatilis, Gray, Turt. Man. 249, t. 10, f. 125. 
On stones in rivulets, common. 
2. A. tacustris, Aull. 
Velletia lacustris, Gray, Turt. Man. 250, t. 10, f. 126. 
On aquatic plants in ponds and ditches, not common.  Prest- 
