FOSSIL MAMMALIA. 7 



desolate plain, which rises towards the flanks of the distant mountain of the 

 Sierra de la Ventana, composed of quartz. On the low shores of this bay, only 

 two places occur, where any section of the strata can be seen ; and at both of these 

 I found fossil remains. 



At Monte Hermoso, a line of cliff of about 120 feet in height, consists in 

 the upper part of a stratum of soft sandstone with quartz pebbles ; and in the 

 lower of a red argillaceous earth, containing concretions of pale indurated marl. 

 This lower bed has the same mineralogical character with the Pampas deposit ; 

 and possibly may be connected with it. The embedded bones were blackened, 

 and had undergone more chemical change than in any other locality, which I 

 examined. With the exception of a few large scattered bones, the remains seemed 

 to belong chiefly to very small quadrupeds. 



In another part of the bay, called Punta Alta, about eighteen miles from Monte 

 Hermoso, a very small extent of cliff, about twenty feet high, is exposed. The 

 lower bed seen at ebb tide, extends over a considerable area ; it consists of a mass 

 of quartz shingle, irregularly stratified, and divided by curved layers of indurated 

 clay. The pebbles are cemented together by calcareous matter, which results, 

 perhaps, from the partial decomposition of numerous embedded shells. In this 

 gravel the remains of several gigantic animals were extraordinarily numerous. 

 The cliff, in the part above high-water mark, is chiefly composed of a reddish 

 indurated argillaceous earth ; which either passes into, or is replaced by, the same 

 kind of gravel, as that on which the whole rests. The earthy substance is coarser 

 than that at Monte Hermoso, and does not contain calcareous concretions. I 

 found in it a very few fragments of shells, and part of the remains of one 

 quadruped. 



From the bones in one of the skeletons, and likewise from those in part of 

 another, being embedded in their proper relative positions, the carcasses of the 

 animals, when they perished, were probably drifted to this spot in an entire state. 

 The gravel, from its stratification and general appearance, exactly resembles that 

 which is every day accumulating in banks, where either tides or currents meet ; 

 and the embedded shells are of littoral species. But from the skeleton, in one 

 instance, being in a position nearly undisturbed, and from the abundance of 

 serpulae and encrusting corallines adhering to some of the bones, the water at 



