54 NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 



Dr. Kobelt in his ' Fauna of Nassau ' remarks on the 

 curious habit of this species, when Uving in the aquarium, of 

 crawling out of the water and affixing the underside of their 

 shells to the glass above the surface of the water. 



P. complanatus seems to be more liable to distortion than 

 others of the genus. In a stream of water pumped from the 

 coal pits at the place variously called Leventhorpe Pastures, 

 Thorp Hall Pastures, and Waterloo, an abundance of curious 

 and variously contorted specimens were obtained about 1865 

 by several collectors. This place has not been examined for 

 some years, and it is possible that these peculiar shells may be 

 still obtainable at the same place. 



Dr. Gray remarks on the tendency of this species to dis- 

 tortion when living in the ponds of warm water emitted from 

 steam engines in Yorkshire. 



In May, 1885, Mr. Knubley found this species abundantly 

 in a subfossil state in a deposit two feet below the surface on 

 the banks of the River Tutt, two miles south of Boroughbridge. 

 It is also found on the moles' hills, and on the arable land at 

 Askern. 



Specimens of a Planorbis from Clarence River, New South 

 Wales, named by Mr. Edgar A. Smith, of the British Museum, 

 Planorbis ohtusns Desh., do not seem to differ in any material 

 degree from our species. Further observations on this point 

 are desirable. In his Monograph of the Freshwater Shells of 

 Australia, published in 1881, Mr. Smith gives Adelaide as the 

 locality of P. obtusus, on the ground that four specimens in 

 Cuming's collection have a label Adelaide attached to them. 



3. Vale of York — York, 1871, W.H.B. ; very common about York, W.C.H., 

 1879 ; very abundant about York, and found in most suitable 

 ponds or ditches, Askham, Hobmoor, R. Foss, Bishopthorpe Ings, 

 ditches round Huntington, &c., R.M.C., 1881 ; Knavesmire, July 

 13th, 1880 ! Bootham Stray, 1857, W. Whitwell ! several in ponds 

 in corners of fields, York, R.M.C., 1883! plentiful in a small 

 reedy ditch-expansion by left side of Foss, above Yearsley Bridge, 

 1858, VV. Whitwell ! pond near York, W. West, 1881 ! Bishop- 



Trans.y.N.U., 1884 (pub. 1SS6). Series C 



