IO PATAGONIAN EXPEDITIONS PALAEONTOLOGY. 
Trigonia subventricosa belongs to a purely Cretaceous section which 
has similar forms in the Upper Cretaceous, but the most closely relatep 
form is T. ventricosa from the Lower Cretaceous Uitenhage beds, which 
also yield a form similar to the other Pueyrrydon species T. heterosculpta , 
though another species which may belong to the same section occurs in 
the Upper Cretaceous Quiriquina beds of Chili. The evidence of both 
Ammonites and Trigonias, therefore, seems to favor the Lower Cretaceous 
age of the series. 
The specific characters of some of the other groups, such as the Ostrea, 
the Gervillia, the Astarte species, the Pleuromya, and the Solecurtus (?) 
also tend to place the beds below the middle of the Cretaceous. Certain 
of the other forms, such as Cinulia, Tornatellasa, Lunatia, Martesia, Turnus, 
Mactra (?), and Pinna, have a more modern aspect and would not be out 
of place in an Upper Cretaceous fauna, while the remainder are mostly 
of types that have a' greater range within the Mesozoic. 
After my preliminary examination of this collection the opinion was 
expressed 1 that the horizon represented is “about the middle of the Cre- 
taceous, at least not lower than the Gault.” This judgment was influ- 
enced to some extent by the supposed occurrence in the collection of the 
characteristic Upper Cretaceous genus Pugnellus. Further study of the 
material after it was better cleaned showed that this generic identification 
was incorrect, and the closer examination of the collection has in several 
cases tended to emphasize the evidence for older rather than newer Cre- 
taceous age. The former opinion is, therefore, now modified to this ex- 
tent, that the horizon is not later than the Gault. Although the evidence 
as above sketched and as given more in detail in the specific descriptions 
does not seem to me to justify the definite reference of the Pueyrrydon 
series to any one of the European Cretaceous horizons it is reasonably 
certain that it belongs within the Lower Cretaceous and is not younger 
than the Gault. 
1 Quoted by Hatcher, Am. Jour. Sci., 4th Ser., Vol. IX, p. 90, and published in abstract 
of communication to Geological Soc. of Washington, Science, N. S., Vol. XI, p. 349, 1900. 
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