201 



NOTES ON 

 PLANORBIS AND MARGARITANA IN ICELAND. 



HANS SCHLESCH. 

 Hellerup, Denmark. 



It is noteworthy that these genera have not been found in 

 Iceland for nearly fifty years, and the species may be looked 

 upon as either of doubtful occurrence or of only temporary 

 introduction, except Planorbis arcticus Beck, which also lives 

 in Greenland, Northern Scandinavia and Finland. 



Planorbis (Gyrorbis) leucostoma Mill. (=rotundatus Poiret). 

 W. Reykjavik Tjornin (Steenstrup and Hallgrimsson)* 

 Laugarnar near Reykjavik, 1868 (Gronlund). 

 Planorbis (Gyrorbis) spirorbis Linne. 

 W. Reykjavik, 1877 (Th. Thoroddsson, spec, in Reykjavik Mus.) 

 Planorbis (Gyraulus) glaber Jeffreys. 

 Recorded from Iceland by Westerlund (Synopsis Moll. 

 Extram. Scandinav., 1897, p. 122). 



Planorbis (Gyraulus) arcticus Beck. 

 N. Myvatn, 1876 (Th. Thoroddsson, spec, in Reykjavik Mus.). 



Margaritana margaritifera Linne. 

 W. Reykjavik, 1863 (Israel). 



Remarks : The well-known Unio collector, the apothecary 

 Israel wrote (20th March, 1914) to me about this interesting 

 find, ' I have in my collection a specimen, big, thick-shelled, 

 plump form, which my father found living in a streamlet 

 near Reykjavik in the year 1863, while he was a private 

 teacher in the house of a Danish nobleman.' 



-: o :■ 



Mr. W. N. Cheesman, J. P., has presented a collection of myxomycetes 

 to the Botany department of the Leeds University. 



In a paper on ' The Development and Morphology of the Ammonite 

 Septum, ' by Prof. Swinnerton and Mr. Trueman, recently read to the Geo- 

 logical Society of London, two methods of studying the septum (not 

 merely the suture) were used : — (1) Cleaning the face of the septum com- 

 pletely ; (2) filing away the surface of the whorl in successive layers, and 

 thus making a series of sections — called septal sections — of the septum 

 parallel to its periphery. 



We have just received The Lancashire and Cheshire Naturalist for 

 February and March, which completes Vol. IX. As these ' have been 

 turned out almost entirely by one pair of hands,' it would perhaps be 

 unkind to criticise the typography ; to prevent mistakes in binding, 

 however, it is as well to point out that the first page in the February 

 issue should be 281, not 261. Among the subjects discussed are Midge- 

 Galls ; Arachnida ; Ornithology ; a record of a rare wood-louse (Porcellio 

 ratzeburgii) ; Mite-Galls ; ' Castration-Parasitaire ' in insects ; Nature 

 Study in Schools ; School Gardens ; Querns in North Wales ; The Charles 

 Bailey Herbarium ; and Oikogetons. Most of the papers refer to Lanca- 

 shire or Cheshire. 



1917 June 1. 



