﻿48 BULLETIN 103^ UNITED STATES NATIONAL MUSEUM. 



Specimens of foraminifera numerous and well preserved, rep- 

 resenting an off-shore assemblage comparable to 6035. 

 5850. — Near Mount Hope — Pleistocene. 



Loose shells and marl obtained from ditch through swampy 

 ground about one-fourth mile from present sea beach and 

 about 6 to 8 feet above high tide. 

 Contains a few foraminifera of common shallow water, tropical 

 species. 

 The geological position of certain material from near the Atlantic 

 end of the canal seems from the evidence of the contained foramin- 

 fera to be younger than the position previously assigned to it — the 

 upper Oligocene. , By a reference to the table of distribution it will 

 be noted that the great majority of the species occurring at the sta- 

 tions in question; 6533c, 6035, and 6036, do not occur in the ma- 

 terial of definitely Oligocene age. In such cases as that of Cristel- 

 laria rotulata there is a slight difference in the specimens from these 

 stations and those from the Pacific side, 6010, 6012a, 6012c, but the 

 specimens at the latter stations were in small quantity, and the dif- 

 ferences could not be made use of, mainly from lack of a sufficient 

 number of specimens. In the case of Cristellaria vaughani this 

 seems to be a well-characterized species occurring at several stations, 

 but even in it there are very minor differences. Among the species 

 of Glohigenna, the more generalized species such as G. bulloldes, 

 which has a very wide geological range, occur more or less constantly 

 throughout the collections, but the strongest evidence comes from 

 the last tliree species and OThulina, which are very rarely found 

 fossil, and then only in the very latest tertiary. These were Avell 

 characterized species, the specimens are very clean and complete, and 

 resemble a modern Globigerina ooze of considerable depth. The 

 three species of Pulvinulina also occur nowhere but at these stations. 

 Pulvinulina concentrica is essentially a recent species and P. me- 

 nardii is characteristic of modern Globigerina ooze. Sigmoilina 

 tenus and S. asferula are also speces of recent Globigerina ooze of 

 moderate depths. On the other hand, the lack of certain things is 

 also significant. Ampliistegina, which occurs more or less regularly 

 in the other portion of the material, is entirely wanting in the three 

 Pacific stations, 6033c, 6035, and 6036. Polystomella also does not 

 occur. Both the last two genera are very characteristic of the 

 coastal plain Oligocene of the United States. It may be argued in 

 this case, however, that the stations were originally too far from 

 shore to have these genera which are more characteristic of shallow 

 littoral conditions. 



On the whole, the foraminifera bear out the geological determina- 

 tions based upon the other groups of organisms. 



