LAND AND FRESH-WATER SHELLS. 183 
Planorbis carinatus.— Common and well distributed. Askham, 
Hobmoor, the Foss, &c., are its localities. 
Planorbis complanatus—Very abundant. Found in most 
suitable ponds or ditches. Askham, Hobmoor, the Foss, Bishop- 
thorpe Jugs, ditches round Huntington, &c. It is much subject 
to monstrosity ; one was obtained at Bishopthorpe which rose in 
the centre like a cone, and another I got near the Foss had the 
whorls very much distorted. 
Var. rhombea.—A few in a pond at Bishopthorpe, and in one 
of the Hobmoor ponds. This must be distinguished from the 
young, which also has little or no keel. 
Planorbis corneus.—Clifton (H.)  Strensall, Askham, Hob- 
moor, stream beside the Foss, Bishopthorpe, &c. Common. 
Especially good at times near the latter place. The very young 
specimens have a curious appearance, being hairy. 
Planorbis contortus.—Pretty common. Abundant, but always 
small, both at Askham and Hobmoor. Larger, however, at 
Bishopthorpe. Thousands upon thousands of exceedingly fine 
specimens live in a tiny pond—than which I never saw a filthier— 
near the south end of Scarborough railway-bridge. 
Physa hypnorum.—Very abundant indeed in the York district, 
and, I think, unusually fine. In vast numbers in a certain pond 
at Bishopthorpe, where I could obtain it by handfuls one summer, 
when it was dried up. One individual actually measured four-fifths 
of an inch in length. Also common in the ditches there, by 
Acomb Wood, the stream on Clifton Jugs, the small ditch where 
I found P. pusillum so numerous, a dirty ditch beside the public 
footpath to the north end of Scarborough bridge, Poppleton, 
Bootham, Tillmire, Strensall, Knavesmire, and elsewhere. Pond 
near Burton Lane, Clifton (R.) 
Physa fontinalis.—Decidedly less common than the last species 
mentioned. Unusually fine in the Foss, near Huntington (H.), 
and at Hobmoor. Also found at Askham, Bishopthorpe, and 
many other places. 
Limnea peregra.—Of course found in the greatest abundance. 
A ditch that produces nothing else will certainly yield this. 
Doubtless many other named varieties occur, but I have not 
studied them sufficiently to be able to identify them. One I kept 
in captivity deposited two lumps of spawn, containing about 280 
eggs altogether, upon the glass on the 19th May, 1877. These 
