ioo MOSTLY MAMMALS 



the whole of the short sole touches the ground in the 

 ordinary manner. An important difference from the sloths 

 is to be found in the circumstance that the bones of the 

 terminal joints of the feet have a longitudinal median groove 

 on the upper surface at their tips. 



With these remarks on some of the leading features of 

 the sloths and ant-eaters, the reader will be in a position 

 to appreciate the peculiarities in the structure of the ground- 

 sloths, and likewise to understand the appropriateness of 

 the name by which they are designated. 



Apparently the first of these extinct animals known in 

 Europe was the giant ground-sloth, or Megalotherium, of 

 which a nearly complete skeleton was discovered in the year 

 1789 near Lujan, in the province of Buenos Aires. This 

 skeleton was soon after sent to Madrid, and described by 

 Cuvier in 1798, who gave it the name by which the animal 

 has ever since been known. Cuvier recognised the affinities 

 of the megalothere to the sloths ; and other skeletons sub- 

 sequently obtained from the superficial deposits of Buenos 

 Aires, and which are now in the Museum of the Royal 

 College of Surgeons, the British Museum, and the museums 

 of Milan, Paris, and La Plata, have in their turn served to 

 confirm the general truth of the original determination. 



One of the most gigantic of land mammals, measuring some- 

 where about eighteen feet in total length, the megalothere, 

 although with a more elongated skull, agrees with the sloths 

 in the number of its teeth. In structure, however, these 

 teeth are decidedly different from those of the sloth. In 

 form they are square prisms, with a length of over ten 

 inches, and a diameter of fully an inch and a half. The 

 summit of each tooth carries a pair of transverse ridges, 

 produced by the alternation of vertical plates of different 

 hardness in the tooth itself ; and since the teeth are rootless 



