April 1, 1874] 



NATURE 



419 



Fort Bridger is a military post about 100 miles E.N.E. 

 of Great Salt Lake City, in the south-west corner of the 

 Wyoming Territory. The valley in which it is situated 

 stands nearly 7,000 ft. above the level of the sea at the 

 base of the Uintah Mountains, which form its southern 

 boundary ; the Wind River Range defining it on the 

 north-east, and the Wahsatch Mountains on the west 

 separating it from the Great Salt Lake. The enclosed 

 plain is evidently the remains of an extensive fresh-water 

 lake, which in the Eocene period must have abounded 

 with animal life, and whose borders must have been the 

 haunts of animals, both huge and small, which lived and 

 died by its marshy banks. Green River now runs through 

 the plain, and it, with its smaller tributaries, by cutting 

 up the easily eroded deposit, produces a scenery of a 

 most peculiar character, consisting of flat-topped hills 

 and cliffs, with perpendicular sides, and often most gro- 

 tesque proportions. Those of the water-courses which do 

 not dry up during the summer months are fringed with 

 vegetation, such as cotton-wood, willow and aspen trees, 

 but most of the country is treeless and barren, reminding 

 the spectator more ot the ruins of a colossal city, than of 

 any other existing scenery. 



The flat-topped hills, table-lands, and scarp-rocks are 

 termed " buttes," and the fossils are generally found at 

 their bases, having fallen there from the gradual at- 

 mospheric disintegration of their sides, along with the 

 debris of the deposits. The fossils consist mostly of the 

 bones and teeth of vertebrata, together with lacustrine 

 shells. The bones are generally black or brownish, 

 sometimes yellowish ; they are generally distorted and 

 much broken, except the small ones, such as those of the 

 carpus and tarsus. They do not withstand the action of 

 the air at all well. 



The remains of mammals, which are very abundant, 

 are mostly of genera which are not found elsewhere. 

 Several, however, approach those of the Paris tertiary 

 basin. The odd-toed Ungulata, or Perissodactyla, are 

 particularly numerous, whilst even-toed Ungulate or 

 Artiodactyla are as remarkably few. True Proboscidians 

 are not found, but if Prof. Marsh is correct in placing 

 Dinoceras in an order by itself, animals equally huge, of 

 an independent type, were far from uncommon. Most of 

 the other mammalian orders are most probably repre- 

 sented, though much has yet to be done in the identifica- 

 tion of specimens. 



Prof Leidy has not yet seen any remains of bird, but 

 we, some time ago, called attention to Prof Marsh's dis- 

 coveiy of Odoiitornis, a bird with well-developed teeth in 

 both jaws ; quite different from Odontopteryx of Owen, 

 which has not true teeth, but teeth-like processes of the 

 jaws. 



The remains of turtles are most numerous ; many of 

 them were aquatic, and some belong to genera which 

 cannot be distinguished from those now existing. What 

 is also particularly interesting to note is that the remains 

 of Crocodilia, which are not very abundant, are all derived 

 from species of true Crocoddus, the old-world form, with 

 the lower so-called " canines " fitting into a notch in the 

 upper jaw, and not from Allii^ator, the genus which is 

 now found in the Mississippi and its nt-ighbourhood, with 

 the lower '■ canine" fitting into a maxillary socket. 



From the large amount of material which has passed 



through his hands, most of which is deposited in the 

 Mufoum of the Academy of Natural Science of Phila- 

 delphia, there are some types of animals which Prof. 

 Leidy has been able to work out in sufficient detail to 

 make his results of general interest. Perhaps the most 

 complete of these is Pal(cosyot>s, a perissodactylate Un- 

 gulate, of about the size of the Tapir, portions of the 

 bones and nearly complete sets of the teeth of which have 

 been several times discovered. The dental formula was 

 complete, the typical forty-four teeth being present, all 



close together in the usual numbers, namely i. ^~ ^ 



3-3, 



c- :,: , P-m. ^~ ^ , m. 3^lJ = 44. The canines were 



I — I 4 — 4 3-3 



peculiarly large, having much the same proportions as in 

 an average carnivorous animal, like the bear. The molars 

 have a resemblance to Pala-otheriiim, the inner lobes of 

 the crowns of the upper molars being, however, more 

 completely isolated. There was a third trochanter to the 

 femur, and three toes, as in the Tapir, were present on 

 the hind feet. Pala:vsyops paludosus is the most common 

 species. It is not known whether the neck was long and 

 curved, as that of Palaotlieriiim is now found to have 

 been, or whether it was short and straight, as in the 

 Tapirs. Limnohyus is a closely allied genus, named by 

 Prof Marsh. 



Another perissodactylate, Hyrachyus, closely resembles 

 Lophiodon of France, but has an extra premolar in the 

 lower jaw, and a lobe less in the last lower true molar. 



Perhaps Ttvi^osus is one of the most interesting of the 

 extinct mammals from the " Mauvaises Terres." It is 

 also perissodactylate, and slightly smaller than the com- 

 mon pig. Its dentition would almost lead to the idea 

 that the long-missing form which may be supposed to 

 connect the Ungulata with the Rodentia, has at last been 

 discovered ; for with the usual complement of molar teeth 

 there are no canines, and a huge pair of rodent-like in- 

 cisors, which, in the lower jaw at least, had an interme- 

 diate pair of very small teeth. The large incisors had 

 persistent pulps, and were formed in part of a circle ; they 

 wore down obliquely, in the same way as in the Cavies ; 

 were grooved longitudinally, somewhat as in Aulacodus, 

 and were covered with enamel on the anterior surfaces 

 only. 



It is not to be wondered at, when small fragments 

 of the skull of an animal so unknown and aberrant as 

 Uintatherium (or Dinoceras of Marsh) were obtained, 

 that each piece should have been referred to a separate 

 genus and species, and Prof Leidy, in the latter part of 

 his memoir, puts together, as parts of UintatJierium, the 

 tusks, horn-cores, &c., as parts of one and the same ani- 

 mal, which he had considered to be portions of different 

 animals in the earlier part of his work, and which he had 

 no reason for associating until Prof. Marsh had described 

 the complete skull of Dinoceras ntirabtlis, which we 

 figured s^me time ago. As we also mentioned at the 

 time, Prof. Cope has also named this genus Eobasileus 

 and Loxolophodon. 



Besides the :(■ ove mentioned, most characteristic forms, 

 some from other territory strata west of the Mississippi 

 River, are described — ungulate, rodent, and carnivorous — 

 many of which are intimately related to those of the Paris 

 basin, and throw further light on them. Prof. Leidy also 



