Near the city of Matanzas,in Cuba, there is a beautiful valley called the Yumuri, of which the good people of the region are justly proud. Its interest to the geologist is unsurpassed in the island. At its entrance there is the most complete section of Tertiary rocks observed by me in Cuba. This valley is a record of the great erosion of the land during most of the Pliocene period, at the close of which it was partly refilled. The valley was reexcavated during the earlier days of the Pleistocene period, and suffered other changes, but it is the closing of the valley into a rock-basininalmost modern days of which I write.

Upon the northern side of the ridges, of which Pan de Matanzas is the highest point (1277 feet above tide), there are the remains of a former plain, which extended five or six miles to near the sea-shore, with an elevation of about 450 feet. Out of this plateau the Yumuri Valley has been excavated with a breadth of about three miles, and length ot five or six miles, with a further rugged extension of one of the tributary valleys teethe foot of Pan de Matanzas, as shown on Map (Fig. 1). The floor of the basin rises from near tide-level to considerable elevations in its upper part, where there are low ridges produced by the unequal washings of the tropical rains.