The relationship between the palaearctic and nearctic faunas 



309 



FIG. 61. Recent and (in Europe) Tertiary distribution of the 

 Mollusc genus Strobilops (Strobilus auctt.) in the Northern 

 Hemisphere. (Outside the map found in South America only.) 



1. Strobilops s. sir. (America) 3. sxxhg. Discostrobilops {America) 



2. subg. Eostrobilops (E.Asia) 4. subg. Enteroplex (Philipp.) 



The figured specimen is of the North American Strobilops 

 (5. str.) labyrinthica Say. 





(After PiLSBRY, 1948.) 



claytoniana L.^) of the American group survived the whole Giinz-Mindel Inter- 

 glacial. 



From investigations in other parts of Europe the persistence of some of the 

 American plants can be followed into later parts of the Pleistocene. Three species 

 of the sedge genus Dulichium, now restricted to America, are recorded from Upper 

 Pliocene (Vlerk & Florschiitz, 1953; Szafer, 1954), two of these survived the 

 first glaciation and one, D. spathaceum Rich., still grew in Denmark during the 

 last (Riss-Wiirm) Interglacial (Jessen & Milthers, 1928, p. 348). The water-fern 

 Azolla filiculoides Lam. likewise persisted into Pleistocene time. Similarly, the 

 fern Osmunda claytoniana, just mentioned, or some closely related non-European 

 form, has quite recently (Lundqvist, 1955, p. 321) been discovered in Swedish 

 deposists from the last interglacial period, 



A very interesting discovery was that reported from "glacial" deposits (without 

 exact dating)^ at Deuben, Saxonia, (Nathorst, 1894), of an elytron of Carabus 



^ Osmunda claytoniana is not strictly American. It still grows in Himalaya and East Asia. 

 2 Woldstedt (1954, p. 248) dates the Deuben fossils as early Wiirm or, possibly, Riss. 



