204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ancient, massive, black igneous rock, showing fully 1,000 feet of verti- 
cally jointed material. According to Professor Wolff's determination 
this is olivine free basalt, or augite andesite, which everywhere seems 
to be the chief species of the older igneous rocks. 
Beyond La Gloria the road seems to have passed the culmination of 
the gorge topography of the Central Mountain masses, and the Atlantic 
slopes of the mountains projecting from the summit of Turialba are 
encountered. The summits or combs of these numerous salients are 
deeply serrated by drainage. At this station more massive igneous 
rocks are seen beneath the superimposed sheets of ash and lava. The 
old red clays again set in in the cuts east of this station, At Tucurita 
(altitude about 3,000 feet) the alpine scenery continues, and the road 
clings to the cliffs far above the river level. 
Disturbed Tertiary Sedimentartes. — A greenish looking flaggy forma- 
tion is encountered near La Gloria, which, from the train, is very sug- 
gestive of disturbed sedimentary rocks. One mile east of the station 
the massive igneous rocks are again encountered. From Las Animas 
(altitude 1,830 feet) to Lajunta (altitude 250 feet), a distance of only 
twenty miles, the road descends through distorted and upturned sedi- 
mentary strata of Tertiary age, as shown in the profiles and sections. 
(Plate VI. Fig. 2.) The igneous rocks protrude in every direction 
through these sedimentaries, and their débris is scattered over the surface. 
This portion of the section clearly demonstrates that the Tertiary rocks 
have been folded and elevated to a height of at least 2,000 feet since 
their original deposition, and that they have been pierced by numerous 
igneous protrusions. ‘These Post-Miocene intrusives are quite distinct in 
specific characters from those of Tertiary age, as will be shown later. 
This section Mr. Sjogren studied in detail. The details on Plate VII. 
show how thoroughly he did this work. The paleontologic and petro- 
graphic determinations of Drs. Dall and Wolff render this section the 
most complete we have of any portion of the Tropical American region. 
At Guallava, the next station east of Las Animas, the Tertiary rocks 
are of Vicksburg age, — according to Dr. Dall, — and, во far as known, 
the only rocks of this epoch west of the Mississippi. At Bonilla Cliff 
they are Upper Oligocene, like the Monkey Hill beds. 
Throughout this portion of the journey tremendous formations of 
rolled boulders also occur, apparently interbedded with the Tertiary 
sediments, and the whole valley of the river is filled with them. The 
Tertiary clays are well shown just east of Torito, one mile beyond which 
point the road and river for the first time emerge out of the gigantic 
