MaucJiesier Memoirs, Vol. Ivii. (191 3), No. 10- 



X. The Variation of Planorbis multiformis, Bronn. 

 By George Hickling, D.Sc, F.G.S., 



Lecturer in Paleontology in the University of Alanchester. 

 {Read March igth, igi2. Received for picblication/tcne ^rd, iQij-) 



Among a collection of fossils which recently came 

 into my possession was a mass of shell-limestone com- 

 posed mainly of shells of the above-named species. The 

 source of the material was unfortunately not recorded. 

 Upwards of five hundred shells of the Planorbis had 

 fallen free from the matrix, most of the individuals being 

 indistinguishable from the various forms from the Miocene 

 of Steinheim, so amply figured by Hyatt. ("The Genesis 

 of the Tertiary Species of Planorbis at Steinheim." Anni- 

 versary Mems., Boston Nat. Hist. Soc, 1880.) In some 

 individuals the spire attains a still greater height than in 

 any of Hyatt's examples. 



The occurrence of all the specimens here considered 

 in a single lump of material naturally raised the question 

 whether they were all referable to a single species. If 

 the photographs of the accompanying plates are com- 

 pared with those of Hyatt's plate 9, it will be seen that 

 the shells now described include representatives of several 

 of Hyatt's species and sub-species, some of which are 

 stated to be confined in the Steinheim deposits to distinct 

 horizons. In my own material it was readily noticeable 

 that forms with moderate spires were abundant, while 

 extreme forms — z>., those which were flat and those which 

 had high spires — were rare. This would obviously be the 

 case if we were dealing with an example of extreme con- 



Aupist 2'jth, igij. 



