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PATAGONIAN EXPEDITIONS ! PALAEONTOLOGY. 
Glycimeris ibari. Crepidula gregaria. Mur ex hatcheri. 
Lucina promaucana. Natica darwini. Marginella gracilior. 
Dosinia meridionalis. 
Miocene and Pliocene relations: 1 species =1.5 per cent. 
Calliostoma iheringi. 
Pliocene and Recent relations : 2 species = 3 per cent. 
Gibbida dalli. Marginella olivella. 
To sum up, among the species which may be compared with known 
ones, the percentage of the relations with particular beds is the following : 
Cretaceous 4 % • • 
4 % 
Eocene 7 
Oligocene 10 
Eoc. and Olig 1.5 
Eogene 18.5 
18.5% 
Intermediate 12 
12 % 
Miocene 32 
Pliocene 6 
Recent 4 
Mioc.-Rec 19 
Mioc. and Plioc 1.5 
Plioc. and Rec 3 
Neogene 65.5 .... ^5.5% 
100 % 
The above figures speak for themselves. We see a constant increase 
of the percentage from the Cretaceous to the Miocene, and then again 
quite a sudden decrease from Miocene to Recent. The percentage of all 
Neogene forms is 65.5, considerably more than half of the number, while 
that of the Eogene and Cretaceous together is only 22.5 ; the rest (12 per 
cent.) is intermediate between Eogene and Neogene. 
These facts bring the Patagonian beds undoubtedly into the Neogene , 
and when we consider the fact that after the Miocene there is a marked 
decrease in the percentage, we must put these beds in the beginning of 
the Neogene times, that is to say, in the Miocene. This course is ren- 
dered the only possible one by the fact that 32 per cent, of the whole 
number of species shows Miocene relations. No other group has a per- 
