176 



MEGASPIRID^:. 



the Eocene in western Europe, and shortly thereafter became 

 extinct, either in consequence of over-specialization, or as a 

 result of physical changes in the unstable geography of this 

 area. The ancestors of Perrieria and C&locion made their 

 way southeastward to Papua and Australia, like many other 

 and later groups. The Brazilian Megaspira traces its fore- 

 bears over the mid- Atlantic, like the Streptaxidce, Ampul- 

 lariidce, various fresh-water fishes, etc., of the same region, 

 from tropical Africa, whence they migrated to South Amer- 

 ica over the Cretaceous land-bridge now held by an increas- 

 ing number of zoo geographers to have spanned the Atlantic 

 (see Pilsbry, Man. Conch., Classification of Bulimulidce, p. 

 ix, Oct., 1902; and especially, Ortman, Proc. Amer. Philos. 

 Soc., xli, 1902, 350). 



The exigencies attending the existence of a type which had 

 evidently attained a highly specialized polygyrate, internally 

 lamellate shell before the close of Mesozoic time, have left but 

 a few widely scattered genera, represented by but few species ; 

 and one monotypic group, Ccelocion, by its senile character^ 

 istics is apparently on the verge of extinction. 



The phylogenetic views here submitted may be represented 

 diagrammatically thus: 



Megaspira 



Clausiliidae 



Cretaceous 



Kocene 



Recent 



