566 



SCIENCE. 



[N. S. Vol. XXIV. No. 618. 



genera, so that, as a rule, Merycoidodon can 

 be distinguished by the teeth alone. 



EucROTAPHUS Leidy. 

 Proceedings Academy of Natural Sciences, 



Philadelphia, Vol. V., 1850, p. 90. 

 Type Eitcrotaphus jacksoni Leidy. 



The type specimen is the posterior portion 

 of a skull in the Academy of Natural Sciences 

 in Philadelphia. According to the label it 

 comes from near Fort Laramie, Wyoming, 

 and was presented by Alexander Culbertson. 

 The type specimen is distinguishable from 

 Eporeodon by peculiarities in the basal por- 

 tion of the skull; and, so far as I have ob- 

 served, the more complete specimens with 

 large buUse from the region of the plains are 

 different from those of Oregon; therefore it 

 seems best at present to consider them as be- 

 longing to separate genera. In the type of 

 Eucrotaphus the tympanic bulla is large and 

 symmetrically rounded, the paroccipital proc- 

 ess is intermediate between that of Merycoi- 

 dodon and Eporedon, being more transverse 

 and laterally expanded at the base than in the 

 former and less than in the latter. There is 

 no lamina of boties separating the pit for the 

 tympanohyal from the stylomastoid foramen 

 as in Merycoidodon. The external auditory 

 meatus is trumpet-shaped and not greatly en- 

 larged as in Eporeodon. 



Eporeodon Marsh. 

 American Journal Science (3), IX., 1873, p. 



249. 

 Type Eporeodon occidentdlis Marsh. 



A skull from John Day River, Oregon. 

 Presented to the Yale Museum by Rev. 

 Thomas Condon. 



Marsh evidently failed to mark the type, 

 but only one skull in the Condon collection 

 corresponds to the type as Marsh designated 

 it. The bullae are inflated. The paroccipital 

 processes are transverse and moderately ex- 

 panded laterally and are not so prismatic be- 

 hind the buUfe as in Eucrotaphus. The two 

 genera are readily distinguishable by the 

 forms of the external portions of the tym- 

 panies. In Eporeodon the external auditory 

 meatus occupies a large space between the 



postglenoid and paroccipital processes. There 

 is a deep pit for the tympanohyal and it is so 

 placed that it looks almost like an inner open- 

 ing to the external meatus. There is no pit 

 for the mastoid foramen. The outer portion 

 of the external auditory meatus is expanded 

 anteriorly into a wing in other specimens of 

 Eporeodon, and I think it is also thus ex- 

 panded in the type, though my notes do not 

 state the fact. Most of the John Day skulls 

 are flattened on top and the upper contour 

 of the skull is nearly straight. This usually 

 serves at a glance to separate Eporeodon from 

 Eucrotaphus, but occasionally there is a skull 

 from the John Day formation more like those 

 of Eucrotaphus. 



Mesoreodon Scott. 

 Type Mesoreodon chelonyx Scott, American 



Naturalist, Vol. XXVII., 1893, p. 661. 



The type, which is contained in the Prince- 

 ton Museum, is a skull and mandible with a 

 large portion of the skeleton. It was obtained 

 in the lower Deep River (Fort Logan) beds 

 in Smith River valley in Montana. The skull 

 is still partially enclosed in a hard matrix, so 

 that some- of the characters, which distinguish 

 the previously mentioned genera, can not be 

 clearly made out in this specimen. The skull 

 is rather high, not depressed vertically as in 

 Eporeodon. The teeth are not high, but ac- 

 cording to Scott the molars show * an in- 

 cipient tendency to hypsodontism.' The par- 

 occipital processes are expanded laterally 

 above, are prismatic below and are in contact 

 with the tympanic bullae anteriorly. The 

 external and auditory meatus is long, straight, 

 directed upward as well as outward and back- 

 ward, and has anterior wings in contact with 

 the postglenoid processes. It probably can be 

 distinguished from Eporeodon by its larger 

 size, higher skull, the different form of the 

 squamosal processes of the zygoma, and the 

 different form of the tympanies. 



Promerycocho]:rus Douglass. 

 Type Promerycochoerus superhus Leidy, Amer- 

 ican Journal of Science, January, 1901, p. 

 82. 

 From the upper John Day beds, Oregon. 



