74 AMERICAN SPECIES OF VERTIGO. 



and of highly peculiar species in the Bermudas and Bonins 

 outlying, degraded old volcanic masses which have been base- 

 levelled and further reduced by subsidence indicate a long 

 period of evolution in the northern continents. Its absence 

 in the Atlantic archipelagos Azores, Madeira, etc., is per- 

 haps due to belated arrival of Vertigo proper in extreme 

 western Europe. There are a few Eocene species probably 

 belonging to the Vertigininae, which indicate the presence of 

 the subfamily in western Europe prior to the Oligocene. 

 The single genus Stawrodon in Madeira points in the same 

 direction. 



The species of Vertigo are considered in four groups : 



I. American species. 



II. Species of Japan and the eastern border of Asia. 



III. Palaearctic species of Europe, Asia and northern Africa. 



IV. Tertiary species. 



I. AMERICAN SPECIES OP VERTIGO. 



After the early work of Say and A. Binney, the American 

 Vertigines were studied by Dr. Gould, and twenty years later 

 by Professor E. S. Morse, who was a pioneer in the critical 

 study of our minute land shells. His results, published in 

 various papers between 1864 and 1868, were incorporated 

 by W. G. Binney in his Terrestrial Mollusks vol. V, becoming 

 a permanent addition to science. In 1889 Dr. V. Sterki pub- 

 lished the first of a long series of papers on Pupillidas which 

 have made him the first American authority on the subject. 

 We owe to him the discovery of many of the most remark- 

 able of our Vertigos, and also valuable critical work on the 

 older species, their mutations and races. Many collectors 

 were induced by him to search for the small Pupillidse, with 

 gratifying results. 



In the preparation of the following monograph the author 

 has had frequent occasion to consult Dr. Sterki. It will be 

 seen that his published work, letters and MS. notes have been 

 quoted freely ; and the monograph is much the better for his 

 generous assistance. In every case Dr. Sterki 's contributions 

 have been acknowledged in the text. 



