176 



MEGASPIRID^E. 



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 Ccelocion 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 zoogeographers 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, Ccrlocion, by its senile character- 

 istics is apparently on the verge of extinction. 



The phylogenetic views here submitted may be represented 

 diagrammatically thus : 



Megaspira 



Cretaceous 



Koceiie 



Eecen' 



