xliv GEOGRAPHIC DISTRIBUTION. 



Several Eocene species from Utah and Wyoming are probably refer- 

 able to Epiphragmophora ; and perhaps the Miocene Helix leidyi 

 Hall & Meek belongs here also ; though the condition of preserva- 

 tion of these fossils of the fresh -water strata of the West, is quite in- 

 sufficient for positive generic identification, which must await the 

 finding of more perfect material. 



Returning to the Palsearctic region, we observe that a few species 

 of Eulota have penetrated into Central Asia, and one, E. frvticwn, 

 as far as eastern Europe. This form is evidently a late-comer, 

 being absent from the loess fauna, and belonging to a section of 

 Eulota characterized by the degeneration and loss of the flagellum. 

 Its late advent in Europe may be correllated with the presence in 

 China of a few European types such as Helicodonta and Metodontia. 



The Belogona Siphonadenia are par excellence the Helices of Eu- 

 rope. Judging purely by the present distribution of the group, its 

 diagnostic peculiarities seem to have been assumed in the European 

 or adjacent tracts, whither the ancestral stock of Belogona Euadenia 

 had emigrated from the Orient. Probable companions of these 

 Belogona were the terrestrial operculates (some of which have been 

 erroneously referred to West Indian genera), and perhaps the Agn- 

 atha, although the origin of these is problematic. In this European 

 extension of the Palsearctic fauna the Siphonadenious phylum has 

 split into numerous genera, and apparently has crowded out any 

 earlier Helices of simpler structure, if such ever existed in that 

 quarter of the world. The old families Endodontidce and Zonitidce 

 retained their place owing probably to the notably different stations 

 occupied by them. Very early branches of the European Belogona 

 were Leucochroa, a probable remnant of the original stock which 

 did not share the changes resulting in modern Siphonadenia; and 

 Vallonia, a genus well differentiated in the early Eocene of Europe, 

 now more widely dispersed than any other genus of Helicidce, and 

 possibly antedating the European immigration. Further notes upon 

 the Belogona Siphonadenia will be found on pages 235-237. The 

 only Siphonadenia which have strayed far from the area now 

 occupied by the majority of the genera, are certain Chinese forms 

 referred to Helicodonta and Hygromia (q. v.), which from their close 

 resemblance to European types are probably recent colonies moving 

 eastward through Siberia. Thus, Metodontia seems closely allied to 

 Dibothrion, a group of middle Europe and Siberia ; and H. bicon- 

 cava of China is nearly allied to the European Miocene H. involuta 



