I n the north-eastern part of the island of San Domingo, at an average distance of about 30 miles from the sea, runs a range of mountains with an east and west direction, consisting of mica schist. Between this range and the northern sea an extensive tertiary formation occurs, being about 30 miles broad, and at least 100 miles in length from east to west. It is intersected by several rivers, the principal of which is the Yaqui, on which stands the town of San Jago, distant from the sea about 20 miles, and elevated more than 2000 feet above it. The rivers have cut narrow channels through the strata, which are thus exposed in perpendicular cliffs often 200 feet high. These cliffs near the bottom consist of a bluish sandy shale, whence Mr. Heniker extracted the greater part of the fossils shortly to be mentioned. Higher up the beds become more argillaceous, and contain but few shells, with some corals. This formation is overlaid conformably by tufaceous limestone, which has suffered much denudation, and forms a low range of arid hills, about 500 feet high, resembling chalk downs in their rounded outline, and scantily covered by a dwarfish vegetation. At the foot of these hills, in loose sand covering the shelly deposits, Mr. Heniker found fishes' teeth. These formations dip gently to the N.N.W., and intermediate between them and the sea a red sandstone is found, dipping also to the N.N.W., but at a much more considerable angle. Mr. Heniker