GEOLOGICAL SURVEY OF THE TERRITOEIES. 563 



caused by the fact that tlie Ryrocoidea present the radius of the Prohos- 

 cldia with the hind foot of the Perissodactyla, These animals are, how- 

 ever, well regarded as a distinct order. Whether all the animals to be 

 included in the Prohoscidia possessed a proboscis or not, is of secondary 

 importance. It is nevertheless highly probable that Loxolopkodon and 

 Eobasileus possessed one, and not unlikely that such forms that ap- 

 proach still nearer the tapirs were not without an organ such as they 

 possess, and which Cuvier ascribed to the PaJceotheria and other allies. 



PEOBOSCIDIA. 



One incisor or canine on each side ; molars compound, with postero- 

 anterior replacement; nasal bones abbreviated; astragalus articulating 

 with navicular only; no third trochanter Mephcmtidw. 



Neither incisors nor canines ; molars simple, with vertical replacement; 

 nasal bones shortened; (?) foot; no third trochanter 3inoiheriid(e. 



No incisors; nasal bones elongate; astragalus articulating with both 

 navicular and cuboid; no third trochanter EohasiliidcE. 



Dentition complete, i.e., incisors present; ? nasal bones. Astragalus 

 articulating with both navicular and cuboid; a rudimental third tro- 

 chanter Bathmodontidce. 



These suborders present a series of approaches to the Perissodactyla. 

 Thus the Uohasiliidce agree with the typical Prohoscidia in addition to 

 the above points, in the posterior expansion of the scapula, and its 

 apical acumination ; in the very short cervical vertebrae ; in the flat 

 carpal bones; in the absence of pit for round ligament of the femur; in 

 the flattened great trochanter, contracted condyles, and fissure-like in- 

 tercondylar fossa of the same bone. In the longitudinal crest of the 

 tibia separating glenoid articular faces which are on a transverse line. 

 In the short calcaneum, which is wider than long, and tubercular on 

 the inferior face. In the live digits ; the acetabulum not separated by a 

 peduncle from the iliac plates, and the lack of angular production of 

 the latter beyond the sacrum. Also in the three distinguished sacral 

 vertebrae, as contrasted with* the five closely co-ossified ones of the 

 Eldnocerotidcc. These characters are, some of them, of subordinate 

 value only. 



The chief differences are seen in the cranium, though here also there 

 are important resemblances. Thus, the palate is not excavated be- 

 the molars posteriori}', as is Perissodactyla, nor are the palatine bones 

 produced posteriorly and separated from the maxillaries, as in Artio- 

 dactyla generally. They have a shallow excavation and accompany the 

 maxillaries posteriorly without interruption, as in Eleplias. In Loxoloplio- 

 don the malar bone forms the middle element of the zygomatic arch, send- 

 ing a narrow strip only forward to the neighborhood of the lachrymal. 

 In Uintatherium, according to Marsh, its extention toward the. side of the 

 face is rather greater, much as in some Perissodactyla. The dentition is 

 not far removed from that of Dinotherium, and the mode of succession of 

 the teeth was in all probability similar. The premaxillaries and nasals are 

 excavated and exostosed for the attachment of a trunk in Loxolopliodon. 

 The lateral and occipital crests of the cranium, though diiferent from 

 the enlarged sinuses of the diploe of Elephants, represent the external 

 walls of this structure, and furnish a hint as to its mode of origin, and 

 serve to ease the transition to Perissodactyles. 



The differences in the cranium are consequent upon its anterior elonga- 

 tion, the nasal bones and premaxillaries becoming thus much extended. 

 The lachrvmal is perforated by a small lachrymal canal in Uintatherium, 



