196 bulletin: museum of comparative zoology. 



limestone, I found the massive igneous rock, but not in direct contact. 

 The laminated clays of the Culebra basin outcrop in the railroad cut 

 about 100 yards to the north of the limestones, but whether it would 

 cover or underlie the outcrop of limestone was a point which was abso- 

 lutely indeterminable. From the position of these limestones, however, 

 and the apparent regional northward dip, I am inclined to think that, 

 while overlying the portions of clays of the Culebra section, they are 

 merely a local band of limestones in the greater clay series. 



Here then, indeed, was an old sedimentary fossiliferous rock near the 

 present continental drainage divide, lying about one and a half miles 

 to the east, the outcrop in fact being only 30 feet lower than the rail- 

 road through Culebra Pass, and its fossils would probably throw impor- 

 tant light on the age of the Culebra clays and igneous rocks. Searching 

 the outcrops only traces of a few fossils could be found, — a few small 

 oysters and a single Pecten, 1 — none clear enough to afford definite de- 

 termination. Further study of this material, however, has shown it to 

 contain important microscopic fossils. Sections of the material showed 

 that the limestone is largely made up of foraminifera. Mr. R. M. Bagg, 

 to whom they were referred, says : " Only the slides of No. 14 (the 

 limestone under discussion) were sent, and it is not easy, if possible, to 

 determine anything but generic types in sections alone. These slides, 

 however, contain sections of Nummulites, one Orbitoides, Cristellaria or 

 Eotalia type, and a Nodosaia. It is probably an Eocene rock as in No. 1 

 (the Foraminiferal marls near Bujio, described on page 177), as the 

 Nummulites are the predominating types." 



Thus it will be seen that while there is paleontologic resemblance 

 between this foi'aminiferal limestone of Empire and the foraminiferal 

 beds of Bujio, yet lithologically the materials are quite different. 



The reports of Drs. Dall and Bagg, upon the fossils of the Empire 

 limestone are of value in that they tend to show the apparent Eocene age 

 of the stratified clays to the southward of the Mata Chin section, where 

 direct continuity with the Caribbean section is broken. These beds 

 probably represent a portion of the Eocene series of the Caribbean 

 sedimentaries. 



The Pacific Subsection. 



The slope of the Culebra Saddle with its accompanying clays continues 

 slightly beyond the two Cerros bordering the pass, when they are ab- 

 ruptly terminated by the sudden descent to the Pacific, ten miles distant. 



1 See Dr. Dall's report. 



