HILL: GEOLOGY OF THE ISTHMUS OF PANAMA. 181 
Vamos beds, as shown by Dr. Dall’s report upon the fossils. About 
half a mile south of Gatun on the canal is seen a bluff composed en- 
tirely of green marls, and containing many large and beautiful fossils. 
Otherwise than a few little joints and faults, it has almost a horizon- 
tal structure, dipping slightly coastward. 
Kilometer 9. — The greensand marls continue at the low water line of 
the river, the upper banks being red clay. 
Kilometer 8. — From here on to Colon the canal is mostly cut through 
the swamps, only one more outerop of the older hill structure being 
exposed. 
Kilometer 6. — The canal here cuts the eastern base of the Mindi 
Hills, exposing a bluff over 100 feet in height, which is composed entirely 
of the Tertiary greensand marls previously noted since leaving Gatun. 
Topographically the Mindi Hills are evidently a continuation of the 
Monkey Hill base level, but the strata composing them are older, be- 
longing to the Eocene, while the latter are of the Oligocene age, as shown 
by Dall. 
From Kilometer 5 to Kilometer 3. — After passing the cut through 
Mindi Hill the canal continues through the swamps. Тһе terreplanes 
thrown up by the dredges are all the fossiliferous sandy material dredged 
up from the canal, the bottom of the canal extending to 28 feet below sea 
level, and is the same as the material of the coastal swamps described 
on page 173, and contains innumerable shells of species not older than 
the Pleistocene, many of which are still living in the adjacent water. 
Kilometer 44. — Here the canal touches the land, or inner end, of Nava 
Bay. We stopped to study the swamp formation which here forms the 
interior border of the bay, and ascertained that it is made up of the same 
material previously described along the canal and abounding in the same 
mollusea. The destructive effect of the choppy surf is rapidly destroy- 
ing the coast at this point. 
From kilometer 44 to the terminus at Colon the canal continues 
through the swamp formation. 
Fox River and Manzanilla Bay. — In order to examine further the 
formations of the coast I passed through Fox River and into the rear end 
of Manzanilla Bay, and thence up the artificial cut known as the devia- 
tion, entering the back end of the bay. Тһе swamp lands surround- 
ing the outlet of the deviation for about half a. kilometer of its distance 
are composed of the same recent fossiliferous formation as the Mindi 
swamp and contained similar littoral shells. Inland the deviation passes 
a vertical eutting of over 50 feet, through the base of tho Monkey Hills. 
VOL, XXVIII. — NO, 5. 8 
