FOSSIL EDENTATA OF THE PAMPAS. 185 



Of the Scelidotherium, an allied animal, Mr. Darwin obtained an almost perfect skeleton ; it must 

 have been as large as a rhinoceros ; in the structure of the head, it approaches nearest the Cape 

 ant-eater, in other respects it is related to the armadilloes. Remains of a different species of 

 Mylodon, of another gigantic edental quadruped, and of a large animal with an osseous dermal coat 

 in compartments, very like that of the Armadillo. Of this last, which has been named Glyptodon, 

 there is a very fine specimen in the Hunterian Museum. Teeth and bones of an extinct species 

 of horse, and of an unknown pachyderm, a huge beast with a long neck like the camel. Lastly 

 the Toxodon (so named from the remarkable curvature of the teeth) ; this is perhaps one of the 

 strangest animals ever discovered. In size it equals the elephant or megatherium, but the 

 structure of its teeth shows it to have been intimately related to the gnawers — the order which 

 at the present day includes the smallest quadrupeds. In many details it approaches to the 

 pachydermata ; judging from the position of its eyes, it was probably aquatic, like the Dugong 

 and Manatee, to which it is also allied. 



The beds containing the above fossil remains, consist of stratified gravel and reddish mud, 

 and stand only from fifteen to twenty feet above the level of high water ; hence the elevation of 

 the land has been small since the great quadrupeds wandered over the surrounding plains ; and 

 the external features of the country must then have been very nearly the same as now. 



In another place, Mr. Darwin observes, — " The number of the remaius of these large 

 quadrupeds imbedded in the grand estuary deposit which forms the Pampas and covers the 

 granitic rocks of Banda Oriental, must be extraordinarily great. I believe, a straight line drawn 

 in any direction through the Pampas, would cut through some skeleton or bones. Besides those 

 which I found during my short excursions, I heard of many others ; and the origin of such names 

 as, 'the stream of the animal,' 'the hill of the giant,' is obvious. At other times, I heard of the 

 marvellous property of certain rivers, which had the power of changing small bones into large - 

 or as some maintained, the bones themselves grew. As far as I am aware, not one of these 

 animals perished, as was formerly supposed, in the marshes or muddy river-beds of the present 

 land, but their bones have been exposed by the streams intersecting the subaqueous deposit, in 

 which they were originally imbedded. We may conclude that the whole area of the Pampas 

 is one wide sepulchre of these extinct gigantic quadrupeds." ' 



XL Flint. — Animal Remains in siliceous nodules. — So many beautiful specimens of siliceous 

 petrifactions — that is, animal and vegetable remains transmuted into silex or flint — are figured 

 in the subjoined plates, that it may be useful to offer a few remarks on this subject." In 

 many instances the organic remains in chalk-flints are simply incrusted by the silex; such is the 

 state of numerous sponges which are as it were invested by the flint, and have all their pores and 

 tubes filled up by the same material, the original tissue appearing as a brown calcareous 

 substance. In other examples, the sponge has been enveloped in a mass of liquid flint, and has 

 subsequently perished and decomposed ; in this manner have been formed those hollow nodules, 

 wliicli on being broken present a cavity containing only a little white powder, or some fragments 

 of silicified sponge ; in many instances the cavity is lined with quartz crystals, or mammillated 

 chalcedony. Frequently but part of the zoophyte is permeated by the silex, and the other 

 portion is in the state of a friable calcareous earth imbedded in the chalk. Sponges and other 

 zoophytes often form the nuclei of the flint nodules ; the original substance of the organic 



' Mr. Darwin's Journal, p. 135. The reader interested in these extraordinary fossil remains should visit the British 

 Museum, and the Hunterian Museum of the Royal College of Surgeons in Lincoln's Inn Fields. 

 ' See Wonders of Geology, vol. i. pp. 74—105, for a general view of the process of petrifaction. 



