In this formation the relics of about fifty species of quadrupeds, including the genera _Palæotherium_ (see Fig. 174), _Anoplotherium_ (see Fig. 218), and others, have been found, all extinct, and nearly four-fifths of them belonging to the Perissodactyle or odd-toed division of the order _Pachydermata,_ which now contains only four living genera, namely, rhinoceros, tapir, horse, and hyrax. With them a few carnivorous animals are associated, among which are the _Hyænodon dasyuroides,_ a species of dog, _Canis Parisiensis,_ and a weasel, _Cynodon Parisiensis._ Of the _Rodentia_ are found a squirrel; of the _Cheiroptera,_ a bat; while the _Marsupalia_ (an order now confined to America, Australia, and some contiguous islands) are represented by an opossum. Of birds, about ten species have been ascertained, the skeletons of some of which are entire. None of them are referable to existing species.[7] The same remark, according to MM. Cuvier and Agassiz, applies both to the reptiles and fish. Among the last are crocodiles and tortoises of the genera _Emys_ and _ Trionyx._ Fig. 218: Xiphodon gracile, or Anoplotherium gracile. The tribe of land quadrupeds most abundant in this formation is such as now inhabits alluvial plains and marshes, and the banks of rivers and lakes, a class most exposed to suffer by river inundations. Among these were several species of _ Palæotherium,_ a genus before alluded to. These were associated with the Anoplotherium, a tribe intermediate between pachyderms and ruminants. One of the three divisions of this family was called by Cuvier _Xiphodon._ Their forms were slender and elegant, and one, named _Xiphodon gracile_ (Fig. 218), was about the size of the chamois; and Cuvier inferred from the skeleton that it was as light, graceful, and agile as the gazelle.