46 



NOTES ON PLANORBIS VORTIOULUS, TROSCHEL, AND PL. LMVIS, 

 ALDER; ALSO ON SOME PROPOSED SUBDIVISIONS OF THE 

 GENUS. 



By A. S. Kennaed, F.G.S. 



Read \Qth January, 1908. 



1. Planorbis voeticflus, Troschel. 



The occurrence of this species in the Pleistocene of England was 

 first noted in 1905/ when it was recorded from Grays, Swanscomb, 

 and West Wittering. I am now able to record it from the Cromerian 

 (Forest Bed) of West Eunton, Norfolk, the Holocene of Knettishall, 

 Suffolk, and in a recent state from Pevensey, Sussex. From the 

 Cromerian it is represented by a single example in the collection of 

 Mr. B.B. Woodward, and the specimens from the Holocene of Knettis- 

 hall, Suffolk, were obtained from material sent by Mr. A. May field, 

 whilst the recent examples were collected a few years ago by the late 

 P. Bufford. It may be worthy of record that when this species was first 

 noted in the Pleistocene of Swanscomb Dr. A. C. Johansen told me that 

 he quite expected this species to be found living in England, since on 

 the Continent it was a rare form and was easily overlooked, and I think 

 that this explanation is the correct one. In a fossil state it is perhaps 

 not so likely to be passed over, but living examples might easily be 

 mistaken for immature P. vortex. Now that attention has been called 

 to the form there is very little doubt that it will be found in several 

 of the eastern and south-eastern counties of England. 



2. Planorbis l.^vis, Alder. 



There has always been a divergence of opinion as to the correct 

 name of the shell which has been known in succession as Planorbis 

 IcBvis, Alder, P. glaher, Jeff., and P. parvus, Say. It was first noticed 

 in this country in 1832, and was described by Alder in 1838 as 

 P. Icevis^ and this name continued in use until the publication of 

 Jeffreys' "British Conchology," when it was identified with the 

 previously described P. glaher, Jeff. Since Jeffreys' work was 

 accepted as the standard authority, glaber displaced Icevis until the 

 last few years, when the form has been identified with the North 

 American species P. parvus, Say. The last use of IcBvis in this 

 country that I can trace was in 1899 by Lieut. -Colonel H, H. 

 God win- Austen.^ P. glaber was described by Jeffreys in 1833.* 



He states : " Found with the last [P. albus\ though much less 

 common. It is a much more depressed shell than the P. albus, of 



1 A. S. Kennard & B. B. Woodward, Proc. Malac. Soc, vol. vi (1905), pp. 356-7. 



2 Trans. Nat. Hist. Soc. Northumb., 1838, p. 337. 

 s Proc. Malac. Soc, vol. iii (1899), p. 260. 



* Trans. Linn. Soc, vol. xvi, pp. 387-8. 



