1892.] NATURAL SCIENCES OF PHILADELPHIA. 393 



and finally the peculiar forms of the Atlantic Islands : Ochthephila, 

 Tedula, Craspedaria, etc., etc. 



Here, too, belong the tertiary Helices which authors have always 

 referred to Corydu, Geotrochus, etc., such as H. rugulosa, crepidos- 

 toma, hohemica, hortulana, etc., etc. The sadly mis-named sub- 

 genera Dentellocaracolns and Prothelidomns of Oppenheim also 

 fall into the restricted genus Heli.v, near Macularia and Leptaxis, 

 Hemicycla, etc. Boettger has criticised Oppenheim on the conchol- 

 ogy of his " Palaontologisch-Zoogeographische Stiidie." but his 

 zoo-geographical conclusions and implications are even more erron- 

 eous. It is time that we heard the last of this habit of going to 

 the ends of the earth to find subgenera for the European fossil 

 Helices! With the exception of a few divergent bi'anches which 

 apparently have left no descendants, all of the European tertiary 

 Helices belong to subgenera still occupying some part of the Palfe- 

 arctic realm, or at farthest the Holarctic area. The supposed 

 Corasia, Chlorcea, Eurycratera, Coryda, Dentellaria, Ohha, thloritis, 

 Thelidomus, Mesodon, Triodopsis, etc., which have been reported 

 from the Eocene, Oligocene and Miocene of Europe, belong in no 

 case to those groups, but, for the greater part to the genus Helix 

 as above restricted. Many of them can readily be referred to 

 recent subgenera and sections, such as Camj^ylcea, Gonostoma, 

 and esj^ecially to that primitive stock called " Pentatsenia " by 

 Schmidt and Sandberger, from which sprung the Tachea, Macula- 

 ria, etc., of the recent fauna. 



The East Asian area of distribution is in reality connected with 

 the Eur-African, by way of Siberia, but as the species of the inter- 

 mediate region are few on account of its at present unfavorable 

 climatic conditions, the connection is not effective in preventing 

 divergence of types. We therefore find that the East Asian forms 

 belong mainly to distinct subgenera or sections. The European 

 Eidota, however, is very closely allied to Dorcasia (+ Actista) of 

 Asia ; and the Chinese section Metodontia Mlldff. is scarcely separ- 

 able from Fetasia (H. bidens, etc.) of Europe, We also find closely 

 allied species of Vallonia, Carocolina, etc., inhabiting China and 

 Europe. Besides the above mentioned groups, the following are to 

 be referred here as sections of Helix : Pledotropis Alb., Aegista 

 Alb.,^" Cathaiea Moell., Satsuma Ads., Euhadra Pils. (type H. pel- 

 iomjjhala Pfr.). 



i»See Proc. A. N. S. Phila., 1892, p. 214, pi. 13, figs. G. H. 



