1894. T^HE LA PLATA MUSEUM. 31 



aymaius, which approaches Megatheriuin in bulk, and is characterised 

 by its enormously expanded muzzle and tusk-like anterior teeth, to the 

 comparatively small Scelidoiheviuni leptocephaluni , which is not very much 

 superior to a tapir in size. In the surrounding wall-cases are displayed 

 an almost endless array of skulls, limb-bones, and vertebrae, many of 

 which are associated. Although all the mounted specimens are from 

 the Pampean formation, some of the wall-cases contain examples of 

 the skulls and bones of Scclidothevmm from the somewhat older deposits 

 of Monte Hermoso, near Bahia Blanca. These remains indicate 

 species of much smaller dimensions than those from the Pampean, 

 and thus serve to illustrate the general decrease in the bodily size of 

 the members of the various groups of mammals as we descend 

 from the Pampean beds through the Monte Hermoso deposits to the 

 Santa Cruz beds of Patagonia. This decrease is displayed not only 

 among the Mylodonts, but likewise in the Glyptodonts, and the 

 Macrauchenias, as well as in some other Ungulates. For instance, 

 while the Pampean Mylodonts include species equal to the largest 

 rhinoceros in size, the Monte Hermoso ScelidotJiermm was smaller 

 then a tapir, while Eucholcrops of the Santa Cruz beds was not more 

 than a yard in length, although closely allied to Mylodon. Again, 

 among the Glyptodonts, we notice that some at least of the represen- 

 tatives of the genera Glyptodon and Dcedicitnis from Monte Hermoso 

 were considerably inferior in size to their Pampean successors, while 

 when we reach the Santa Cruz beds we meet with mere dwarfs, as 

 exemplified by the genus Pvopalahoplophorus , of which there is a 

 beautifully-preserved skeleton and carapace in the Museum. 



Reverting to the Pampean Mylodonts, I may mention that' 

 although the time at my disposal did not admit of my undertaking a 

 detailed survey of any of the Edentates, yet I have little doubt that, if 

 this were done, the number of nominal species in this particular 

 group might be considerably reduced. My opinion has already been 

 expressed elsewhere as to the inadvisability of subdividing the true 

 Mylodonts into separate genera, such as Lestodon, Pseudolestodon, and 

 Grypothevmm ; while the proposal to split up the group of Ground- 

 Sloths into several families, instead of including the whole in the 

 Megatheriidae, is not likely to commend itself to English zoologists. 



Perhaps the most striking display in the whole Museum is the 

 magnificent series of the remains of Glyptodonts, which are exhibited 

 in one half of the gallery containing the Mylodonts. Here we see 

 not only a fine array of specimens of the carapace and tail-shield, 

 with or without the skull and limbs attached ; but likewise a number 

 of entire skeletons without the dermal ossifications. These specimens 

 comprise examples of the genera Glyptodon, Pauochthus, Doedicuyus, 

 and the one generally denominated Hoplophoms ; and serve to 

 show conclusively that the original Owenian restoration of Glypto- 

 don was incorrect, the termmal tube of the caudal sheath of an 

 Hoplophoms having been attached to the carapace of a Glyptodon. 



