324 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



and proportion, such as brachycephaly, were one by 

 one added in heredity, so that the offspring of P. leidyi 

 were born on a more specialized heredity plane than 

 those of P. paludosus. P. leidyi was by no means the 

 same animal; it was an enriched stock; it possessed 

 in its germ substance a number of characters not found 

 in its ancestor, and probably it lost some other germ 

 characters. 



Materials. — This species is by far the most richly 

 and abundantly represented in remains of skull, 



type of P. leidyi, a broad-topped skull with lower jaw 

 from Henrys Fork, with a large part of the skeleton 

 associated, level probably upper C. Also the following 

 superior teeth: No. 12208, m'-m\ level C 4; No. 1552, 

 c-m^ left, p^-m^ right, a small female, very progressive, 

 level probably upper C; No. 12196, p^-m' of right side, 

 level C 2; also No. 1565, milk premolars and m'-m^, 

 from Henrys Fork, levelprobably C; in the Princeton 

 Museum, skull and jaws. No. 10009, level probably 

 upper C 



Figure 273. — Skull and head of Palaeosyops leidyi 

 Restoration by Erwin S. Christman made under the direction of W. K. Gregory. 



tooth, and skeleton. The American Museum collec- 

 tions contain the following principal specimens: 

 No. 1516, a perfectly preserved female skull, level not 

 definitely ascertained, probably C 4; No. 12185, a male 

 skull transitional between P. leidyi and P. major, 

 level C 3; No. 1581, a laterally crushed skull with a 

 convex forehead and faint rudiments of the horns, 

 associated with portions of the skeleton (possibly 

 P. rohustus), level probably Bridger C; No. 1544, the 



The best specimen of a lower jaw is that associated 

 with the type skull (No. 1544), certainly a male. 

 There are also Am. Mus. 1585, 1522, 1564, 12200, all 

 probably males; 12197, which is in the milk stage, 

 corresponding closely in size with the upper milk teeth 

 (1565); 5103, possibly a female; and 1549, a female; 

 also Leidy's cotype of P. major (Acad. Nat. Sci. 

 Philadelphia). None of the foregoing lower jaws are 

 positively recorded as to level. 



