NELSON AND TAYLOR: ON YORKSHIRE MOLLUSCA. 53 



' 8 LUCiDUS — Shell of medium size, of a horny amber, 

 transparent, glossy, more compressed, keel very sharp.' 



M. Pascal remarks, ' It is the most beautiful F. carinatus 

 that I have seen.' 

 7. l^ewt k'a/e— Askern, H.S., 1882 ! Sharlston, J. W. 



12. Lower Calder—Ossett, about 1877, J.W. ! 



13. Airedale— Fond at Castleford ! vSwillington Bridge, J.W. 



Var. minor Pascal, 1873. 



This variety is described by Pascal in his ' Catal. des Moll, 

 terr. et des eaux douces du dept, de la Haute-Loire et des 

 Environs de Paris,' as being 11 mill, in diam., and as having 

 an altitude of 2^ mill. 



12. Lower Calder — Mr. J. Hebden in 1874 recorded a dwarf form as oc- 

 curring in a pond near Sandal Castle, which probably w^ould be 

 correctly referable to this variety. 



Planorbis complanatus (L.). 



Abundant in the lowlands. 



Planorbis co7nplanatus is more widely distributed in York- 

 shire than the preceding species, but is also practically absent 

 from the North-Western dales. 



According to Dr. Martin Lister, who wrote in 1678, this 

 species pours forth, when irritated or injured, the same red 

 fluid as Planofbis corneus. 



Mr. Tye says this species is capable of spinning a mucous 

 thread, but does so much less often than Physa and Limnsea. 



Dr. F. Day records, on the authority of Parfitt, that it is 

 occasionally preyed upon by trout, the shells of this and other 

 species having been found in their stomachs. 



