348 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



graphic relations. At La Coca the remains were preserved on the 

 upper surface of a low terrace (pi. 3). The materials were here 

 found weathering out of the thin superficial remnant of mud and 

 gravel, and the spring associated with this occurrence and possibly re- 

 lated to the entrapment is now flowing out from the steeper slopes 

 below the terrace top. This suggests that the shallow ravine below 

 the terrace has been cut since the fossil accumulation was formed. At 

 El Hatillo the picture has a more recent look in that probably there has 

 been less change in the physiography since accumulation of the fossils. 

 Although the surface has a fair slope, the site (pi. 4) is currently a 

 bog and the bones were found near the surface at the periphery of the 

 mud deposit associated with the spring, up to depths of around 7 feet 

 (pi. 7, fig. 1) toward the center of the area where flow of water was 

 greatest. It is of further interest to note that although boggy condi- 

 tions prevail at the present time, no remains of domestic animals were 

 found, such as dogs, oxen, pigs, and poultry — somewhat surprising 

 considering that the immediate area apparently has been well settled 

 for nearly 400 years. 



DESCRIPTION OF THE GIANT SLOTH EREMOTHERIUM 



Like Megatherium, Eremotherium is truly a ground sloth of tre- 

 mendous bulk. It may be compared in size with a mammoth or masto- 

 don but with, of course, rather striking differences in form and rela- 

 tive proportions. The length of the animal's body, for example, was 

 much greater than that of the American mastodon, with a very much 

 smaller head, a longer neck, and a long and massive tail. The length 

 of the vertebral column in a particularly large individual measured 

 over 16 feet (pi. 2) . The hindquarters were particularly robust. This 

 is shown in the striking increase in the size of the vetebrae from the 

 neck back to the sacrum, and the hindlimbs, though a little shorter than 

 in an average-size mastodon, were of much greater width. The femur, 

 for example, while nearly a yard in length, is a few inches shorter 

 than in the mastodon with which comparisons were made, but is 19 

 inches across the distal portion — more than twice that in the mastodon. 

 The comparable parts of the forelimb of the sloth are a little longer 

 than those of the hindlimb but relatively slender by comparison. 



The skull of Eremotherium is about 2 feet long with a comparatively 

 slender snout and rather fantastic processes or bony projections on 

 the arches (fig. 1). The animal had no tusks, but there are five long 

 crowned teeth above and four below, averaging about an inch and a 

 half in diameter. The teeth are of a grinding type with two trans- 

 verse wedgelike crests on each. 



As in other ground sloths the feet of Eremotherium possessed long 

 powerful claws (figs. 2-6 and pi. 1). In locomotion the forefoot car- 



