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BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



shells. This marl is not entirely calcareous, however, but is partly 

 composed of volcanic debris. It has been studied by Mr. H. W. Turner 

 of the U. S. Geological Survey, who reports upou it as follows : — 



" Foraminifera make up the greater part of the sectiou examined. In 

 additiou there are fragments of a slightly greenish augite, and a deep 

 brownish green strongly pleochroic hornblende. A few prisms of feldspar, 

 and very abundant minute clear grains with low gray interference colors 

 presumably also feldspar. The hornblende is brownish (the A ray brown 

 and the C ray deep greenish brown). The augite, hornblende, and feld- 

 spar probably all came from volcanic rocks. " 



At this locality it was impossible to ascertain the stratigraphic rela- 

 tion of this foraminiferal material to the Bujio bluff of igneous material, 

 but from their relative positions it apparently lies unconformably 

 against the latter. Three fourths of a mile below Bujio in the cutting 

 of the canal the same rock crops out, much jointed and so broken that 

 its beds dip as high as 20 per cent in places. This is a more recent 

 and less decomposed exposure of the same foraminiferal beds than at 

 the house of the Chef de Section. One mile below, northwest of Bujio, 

 ■we reached the Chagres, and in the lower part of its banks, composed 

 of red clay, the foraminiferal marls can again be seen at the water's 

 edge in their unweathered condition. 



Crossing the Chagres we came to the plantation of Mr. Shaffer of 

 the Panama Railway Company, who procured canoes to take me down 



Figure 3. Section on Mr. Shaffer's Farm near Pcna Xegra, showing Contact 

 of Foraminiferal Marl with Boulder Formation. 



25 kilometers of the completed canal between this point and I 

 About 200 yards up the river from Mr. Shaffer's house is a hill known 

 as the Pcna Xegra. This is of the same type of topography as nearly 

 all the hills of the Isthmus, sharply pointed, with precipitous slopes, 

 covered with dense vegetation, and is apparently in strike with the hills 



