148 ON THE TOrOGRAPIIY AND CEOLOG\" . 



On the le^'C'l lands north of the hihs there is hut httle niiid, except in a few 

 places where the road runs through strips of woods, but south of a httle settlement 

 called el Valle, the road enters the forest. At first the rolling ground underlaid by 

 alternating strata of shales and thin-bedded sandstones, is not remarkably wet, but 

 as soon as the hills proper are entered the quantit}^ of mud must be seen to be be- 

 lieved. The summit of Loma de los Muertos, half a dozen miles in a direct hne south 

 of Savana-la-Mar, is capped with a not very thicli horizontal deposit of the Miocene 

 limestone similar to that near Cevico, in Avhich I found corals identical with those 

 from the Samba hills, and fragments of the tubes of an undescribed Kii/plms which 

 abounds in tlic j^cllow shales between Esperanza and Guajaibin. Those fossils, 

 though not abundant, amply suffice to fix the age of the formation. The belt, which 

 is a mere cap, is very narrow, and although it apparently unites, .across the trackless 

 hills with the same i-ock at San Lorenzo and on the margin of the Yuma "Valley,. I 

 was able only to draw my deductions by their appearance at a distance. It evidently 

 does not extend very far to the eastward. Its southern margin is soon reached and 

 the clay slates and thin bedded sandstones reappear wherever the unsatisfactory 

 little outcrops show themselves. The two or three miles between the base of this 

 hill and the Savana Grande, are through a swamp of black mud where every traveller 

 avoids, so far as he can, the ti'acks of his predecessors, and where, by the configura- 

 tion of the surface, he is forced into the road " his poor horses flounder belly-deep 

 in mud. Savana Grande is a rolling prairie covered with abundance of grass and 

 inhabited by half a dozen families who live by " taking in " travellers. But Avhere 

 everybody carries his own bed and board, hotel-keeping is not a paying " business^ 

 Horse-feed is their principal source of revenue ; for even the most careless are hardly 

 content to let their horses forage without an extra feed with such a journey before or 

 behind them. Beyond this place a succession of little savanas in the woods, with 

 the regular accompaniment of dry and muddy places, over Cretaceous rocks, takes the 

 traveller a couple of miles, after which he crosses another strip of Miocene similar to 

 the first, except that it here fills the l)asin instead of capping a hill. It is also ver}^ 

 nai-row and but a few feet in thickness, as if it were the thinnino-out edo-e of the 

 deposit. After this, the ground becomes more rolling and drier, and the red and 

 white shales, so often described, appear, bringing with them a different looking 

 country. These continue to a high ridge, the Loma de los Castellanos, where the 

 shales are much harder, some of them almost jaspery. Although the exposures are 

 large and the shales project in many places, especially on the south face of the hilb 

 I have endeavored in vain to decide on a certain measurement of the bedding. Ex- 

 cept the vague statement that the strike, as usual, seems to be nearly east and west, 



