﻿586 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



Rocontly Dr. Sidney Powers has presented to the United States 

 National Museum some specimens he collected at the entrance to 

 Rio Dulco, Guatemala. The rock is a massive light-colored, fine- 

 tcxturod limestone, with a conchoidal fracture, and contains many 

 poorly preserved fossils. Among the fossils are Orbiioliies species; 

 several corals, one of which resembles Siderasirea, another is probably a 

 specimen of Goniopom, and a third seems to be a branching poritid 

 coral that looks prccisoly li]<e a coral obtained by Doctor MacDonald 

 in limestone, referred by him to the Empcrador limestone, in the 

 swamp north of Ancon Hill and about one-quarter of a mile south 

 of Diablo Ridge, Canal Zone; and there are specimens of Osirea, 

 Pecien, and Lima. This matoi'ial is too poor to warrant a positive 

 opinion, but it is worth noting, and it probably represents a hori- 

 zon very near that of the Emperador limestone. 



According to Hill's account of the stratigraphic succession in 

 Jamaica, the correlatives of these uppermost Oligocene deposits aro- 

 represented there by a stratigraphic break, the unconformity be- 

 tween the Montpelicr white limestone and the Bowden marl. 



MIOCENE. 



The definite correlation of the Canal Zone Miocene with European 

 horizons was first attempted by H. Douville in his paper, already 

 cited, on the age of the deposits along the Panama Canal. He 

 sa3-s regarding the deposits overlying those discussed in the fore- 

 going remarks: "Leur age est incontestablement Miocene. "^ He 

 considers the lower part of these deposits as Burdigalian, the upper 

 part as Helvetian in age. That part of the Gatun foimation exposed 

 at Monkey Hill is referred to the Helvetian. 



The literature on the ago of the Gatun formation is considerable, 

 but a lengtliy review of it appears unnecessary. The papers by 

 Toula and by Pilsbry and Brown have already been cited on page 

 560 of tliis volume. Actually there is in most cases more apparent 

 than real discrepancy between the correlations of the different 

 investigators, due to the fact that the Alum Bluff formation, includ- 

 ing the Chipola marl member at its base, has been referred to the 

 upper Oligocene. The Alum Bluff formation is certainly of Miocene 

 age, according to European usage, and is the Am^erican equivalent 

 of the Burdigalian. All available evidence indicates that the lower 

 part of the Gatun formation in the Canal Zone is the equivalent of 

 the Alum Bluff formation of Florida and Georgia. Although the 

 Gatun formation contains numerous species of Foraminifera, echi- 

 noids, and Crustacea, the fauna is predominantly moUuscan, and the 

 discrimination of zones within it must await the completion of the 

 study of the careful zonal collections Doctor MacDonald and I 



> Soc. Gcol. France liall., vol. 26, p. 5U9, 1898, 



