CLASSIFICATION OP OLEACINHXE. XXI 



In Upper Cretaceous, Eocene, Oligocene, Miocene and 

 Pliocene deposits of central and western Europe, many species 

 are found which from their close conchologic resemblance 

 have been referred to the American genera Glandina (= 

 Euglandina), Salasiella and Oleacina. There are no shell 

 characters diagnostic of Euglandina, Oleacina and Poiretia, 

 although these groups are perfectly distinct by characters of 

 the genitalia. The variation in size, sculpture and shape 

 among the European fossil and living forms is not greater 

 than we find among American species of Euglandina or of 

 Oleacina. It seems reasonable therefore to refer all European 

 fossil ' ' Glandinas ' ' to the surviving European genus Poiretia, 

 rather than to distribute them among several American genera 

 as European authors have done. The American genera, it has 

 been shown, have well-defined peculiarities of geographic dis- 

 tribution, which certainly indicate that they are the products 

 of evolution on a progressively disintegrating Mid- American 

 land-area. The genera Oleacina, Varicella, Euglandina and 

 Salasiella must be considered by any one who fairly investi- 

 gates their characters and distribution, to have been differ- 

 entiated largely after the breaking-up of the old Mid- 

 American continent; and it is highly unlikely that species of 

 the European tertiary archipelago really belong to these four 

 geographically characteristic American genera. At the same 

 time, it must be admitted that Europe from the Eocene to the 

 Miocene was largely insular, comparable to the East or West 

 Indies, and evidently like the latter in having numerous 

 parallel phyla in different parts of its interrupted land-area, 

 and among them many phylogerontic groups. Hence the 

 European tertiary Oleacinidcu may be referable to several 

 collateral genera, rather than to the single surviving genus 

 Poiretia ; though no sufficient evidence for this has yet been 

 published. In any case, there can have been no connection 

 between European and American genera since mesozoic times, 

 presumably before the several American genera had been dif- 

 ferentiated. No conceivable scheme of geographic changes 

 could be formulated to justify the reference of European 

 species to Oleacina, Varicella, Salasiella and Euglandina. 



