8 GASTROCOPTA. 



we include Europe, where species existed from Oligocene to 

 Pliocene times, it inhabits every continent, Polynesia and 

 Hawaii, though in these Pacific islands the few species are 

 apparently importations during the human period. North- 

 ward Gastrocopta does not quite reach the 53d parallel, fall- 

 ing far short of the northward range of Pupilla and Vertigo. 

 The absence of species on the American west coast is notable. 



NOMENCLATURE. Species of the genus under consideration 

 formed part of the subgenus Leucochila of von Martens (Die 

 Heliceen, 1860, p. 296), which was a heterogeneous group, a 

 species of the genus Pupoides being designated as type. 



Dr. O. Boettger of Frankfurt, in 1881, was the first to call 

 attention to the composite character of Leucochila. We owe 

 to him the first recognition that Pupa armifera and its allies 

 form a separate genus, which he proposed to call Leuco- 

 chUus. Zoologists at the present time are not agreed as to 

 whether such names as LeucochUus and Leucochila are to be 

 considered distinct; many refuse to accept generic terms dif- 

 fering only in gender termination from prior names, while 

 others hold that they are available. Until some consensus of 

 opinion is reached on this point, and a ruling thereon formu- 

 lated by the International Commission on Zoological Nomen- 

 clature, such similar terms are to be avoided. 



LeucochUus Boettger has been adopted by most German 

 authors who have treated of the genus. In America the spe- 

 cies were left in Leucochila Martens until Dr. V. Sterki, in 

 1891-2, proposed the term Bifidaria, which has been used in 

 practically all subsequent American work on the genus. 



On account of the impossibility of determining whether 

 LeucochUus will eventually be ruled to be a valid name or a 

 homonym, I am reviving the term Gastrocopta Wollaston, 

 1878, which has three years priority over LeucochUus. Wol- 

 laston seems to have had no adequate idea of the limits or 

 characters of his group ; but his first species, Pupa acarus 

 Bens., which I select as the genotype, is closely related to the 

 type of Bifidaria, Pupa servUis Gld. 



AFFINITIES. In both Asia and America there are several 

 genera having the essential apertural structure of Gastro- 



