DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



159 



Figure 90. — Leidy's 

 type of Palaeosyops 

 humilis 



the main cusp there is a large triangular tubercle, 

 with its apex exterior to the fore and aft axis of the 

 crown." (Marsh.) 



Anteroposterior diameter of last upper pre- 

 molar 9 lines [19 mm.] 



Greatest transverse diameter of same 4.25 lines [8 mm.l 



Height of main cusp 6 lines [12.7 mm.] 



Height of posterior tubercle 3.75 lines [7 mm.] 



Synonym. — Canis? marsMi Hay was proposed in 

 place of 0. montanus IVIarsh, name preoccupied by 

 0. montanus Pearson (Hay, 

 1899.1). 



Etymology. — montanus, dwell- 

 ing in the mountains — that is, 

 from the Eocky Mountain 

 region. 



Present determination. — The 

 type specimen of "Canis mon- 

 specimen in the collection of tdnus" is a first lowcr premolar 

 the Academy of Natural of somc Undetermined member 



S c i e n c e s of Philadelphia, <■ ,i n v 



After Leidy, 1S73. Natural 01 t^ie gCnUS FttlaeOSyOpS, pOSSl- 



size. Regarded by Leidy as jjly PaltteOSyOpS paludoSUS Or P. 



"A last upper molar of the . rm p , /-y • 



leftside. • • • Found by mc-jor. ihe reference to Cams 

 Doctor Corson on the buttes ^^Q,s, doubtless made by rcason 



of Dry Creek Canyon." r ,i i . • ii n 



of the deceptive resemblance oi 

 one of the lower premolars to the upper carnassial 

 tooth of a dog. 



Palaeosyops humilis Leidy, 1872 

 Cf. Palaeosyops major, this monograph, page 321 



Original reference. — Acad. Nat. Sci. Philadelphia 

 Proc, 1872, p. 168 (Leidy, 1872). 



Subsequent reference. — Leidy, Extinct vertebrate 

 fauna of the Western Territories, p. 58, pi. 24, fig. 8, 

 1873 (Leidy, 1873.1). 



Type locality and geologic Tiorizon. — "Valley of Dry 

 Creek 40 miles from Fort Bridger (Wyo.)." Doctor 

 Corson, discoverer. "Buttes of Dry Creek Canyon," 

 Bridger Basin; horizon probably Bridger C (Uinta- 

 therium- Manteoceras- MesatirMnus zone) . 



Holotype. — "An upper molar." (See fig. 90.) 



Characters (Leidy). — "An upper molar tooth of this 

 animal measures three-foiu-ths of an inch in diame- 

 ter." In his later description Leidy recognized that 

 the specimen belonged to the milk series. 



Etymology. — Tiumilis, lowly, small; in allusion to 

 the small size in comparison with P. paludosus. 



Present determination. — This milk tooth probably 

 pertains to the genus Palaeosyops, but comparison 

 with P. major and P. leidyi leaves the species unde- 

 termined. 



Palaeosyops Junius Leidy, 1872 



Cf . Mesatirhinus Junius (Leidy) , this monograph, page 388 



Original reference. — Acad. Nat. Sci. Philadelphia 

 Proc, 1872, p. 277 (Leidy, 1872.3). 



Subsequent reference. — Leidy, Extinct vertebrate 

 fauna of the Western Territories, p. 57, no figure, 

 1873 (Leidy, 1873.1). 



Type locality and geologic horizon. — Fort Bridger, 

 Bridger Basin, Wyo.; level not recorded. Dr. J. 

 Van A. Carter, collector. 



Holotype. — -"Doctor Carter recently sent the writer 

 several small fragments of the right side of a lower 

 jaw, together with a sketch of a larger fragment of 

 the left side, containing the last premolar and the 

 succeeding molars." Of this type material only p4 

 (right) and the posterior half of ma (right) were 

 located (1906) in the collection of the Academy of 

 Natural Sciences of Philadelphia. 



Characters. — Leidy writes: 



Intermediate in size to P. paludosus and P. humilis. Founded 

 on portions of a lower jaw agreeing in character with the cor- 

 responding parts of P. paludosus but smaller. Space occupied 

 by the last premolar and the true molars, 4 inches. Antero- 

 posterior diameter of last premolar, 8 lines; of last molar, 

 173^ hnes. 



In the fuller description in his memoir of 1873, 

 Leidy says: 



The specimens * * * appear to indicate a small species 

 of Palaeosyops, though it is not improbable that they pertain 

 to a small variety of P. paludosus. 



The parts agree closely with the corresponding parts of the 

 lower jaw and teeth of the latter, except in size. They have 

 been viewed as representatives of a species with the name of 

 Junius. 



Figure 91. — Leidy's cotypes of Palaeosyops 

 Junius 



Specimens in museum of Academy of Natural Sciences of 

 Philadelphia; Bridger B(?), level doubtful. A, Eight fourth 

 lower premolar (pO; B, posterior part of third lower molar 

 Cms) . Natural size. 



The measurements of the teeth (fig. 91) in comparison with 

 those of P. paludosus are as follows: 



Space occupied by the last pre- 

 molar and molars 



Space occupied by the molars 



Breadth [anteroposterior] of last 

 premolar 



Thickness [transverse] of last 

 premolar 



Breadth [anteroposterior] of first 

 molar 



Breadth [anteroposterior] of sec- 

 ond molar 



Breadth [anteroposterior] of 

 third molar 



Thickness [transverse] of third 

 molar at middle 



39J^ 

 8 



10 

 12 



17 

 7 



[Milli- 

 meters] 



[102] 

 [94] 



[17] 



[12] 



[21] 



[25] 



[10] 



[14] 



55 

 46 



6M 

 12J^ 

 15 

 19 



93^ 



[MUli- 

 meters] 



[116] 

 [96] 



[19] 



[12] 



[38] 



[32] 



[39] 



[19] 



