102 



THE MERYCOIDODONTID.T. 



those of Merycoidodon, are straighter, less arched, and slenderer, while the phalanges are like 

 those of the manus, but larger, and the trowel-shaped unguals have their peculiarities somewhat 

 emphasized. 



Mesoreodon intermedius Scott 1893 

 PI. XI, fig. 3 



Original Reference: The mammals of the Deep River beds. Amer. Nat., XXVII, pp. 659, 661. 



Type Locality: Smith River Valley, Montana. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Type: Holotype, Cat. No. 10416 P.U.M., right Mc. Ill, proximal three-fourths of Mc. IV, proximal and 

 distal phalanges of Mt. Ill, and skull of a very immature individual, with milk dentition. Collected by the 

 Princeton Expedition of 1891. 



Specific Characters: The skull has almost no systematic value, although it indicates affinities 

 with Mesoreodon. 



As compared with M. chelonyx, the metapodials are markedly longer and slenderer, and the 

 keels of the distal trochlea; are more anteriorly extended. The proximal phalanges are much 

 slenderer and more arched than are those of M. chelonyx, and the distal ones are very similar to 

 those of Merychyus but are a little more bluntly pointed. In general, these metacarpals bear a 

 striking resemblance to those of Merychyus, except that the trapezoid facet on Mc. Ill is smaller 

 and there are differences sufficient to exclude this species from that genus. It may be a female, but 

 at present we have no way of determining its exact position. 



Measurements in millimeters 



Mc. Ill — length 69; width 15; width of shaft below head 11. 

 Mc. IV — width of proximal end 13; width of shaft below head 11. 

 Digit III — first phalanx, length 23; width, proximal end 12. 

 Digit III — third phalanx, length 17; width, proximal end 8. 



Mesoreodon megalodon Peterson 1906 

 Figs. 4, 66-67} PI. X, figs. 3-5; PI. XLIV, fig. 1 



Original Reference: The Miocene beds of western Nebraska and eastern Wyoming and their vertebrate 

 fauna-. Ann. Carnegie Mus., IV, pp. 24-26, figs. 2-3. (The specific name is spelled melagodon, which is 

 obviously a misprint.) 



Type Localities: Near Squaw Butte, Sioux County, Nebraska. Paratypal material, in part, collected on 

 Muddy Creek, Hill 66, and Fox Creek Gap, all in eastern Wyoming. 



Geologic Horizon: Lower Miocene (lower and middle Monroe Creek and lower Harrison). 



Types: Holotype, Cat. No. 1325 CM., anterior part of skull and mandible of a young individual, but 

 with permanent dentition. Paratypes, Cat. No. 1323 CM., posterior part of a skull, nearly complete lower 

 jaws, fragments of lumbar vertebrae, fore and hind limbs, and feet; Cat. No. 22-638 A.M., a nearly complete 

 skeleton. 



Specific Characters: The skull has the same general shape as that of M. chelonyx but has 

 a heavier muzzle and lower occiput. The zygomatic arches are wider, and the posterior part of the 

 squamosal processes has about the same size and direction. The malar is approximately the same 

 in depth, but with the squamosal penetrating more anteriorly than in Scott's species. The nasals are 

 longer and are moderately flat. The lacrimal bone is larger, as is also the lacrimal fossa. The 

 frontals are wide and rather flat and extend but slightly in advance of the -pars facialis of the 

 lacrimal. The orbits are large and nearly round. The temporal ridges unite at a point just above 

 the anterior part of the glenoid surface to form a moderately long, thin, and high sagittal crest. 



