NATURAL SCIENCES OF PHILADELPHIA. Ill 



utaries and on both of its principal branches to their sources. Mr. Norris 

 also remarked that the experiment was of much importance in ascertaining if 

 this valuable fish the salmon may not be gradually acclimated in rivers 

 further south than those they now frequent. 



Oct. 18th. 

 The President, Dr. Ruschenberger, in the Chair. 

 Twenty-one members present. 



Prop. Leidy directed attention to a collection of fossils, recently received 

 for examination, through the Smithsonian Institution, from Rev. Thomas 

 Condon, of Dalles City, Oregon. The fossils consist of remains of mamma- 

 lia, obtained by Mr. Condon from the valley of Bridge Creek, a tributary of 

 John Day's River, Oregon. They appear petrified in the same manner as the 

 similar remains from the Mauvaises Terres of White River, Dakota, but gene- 

 rally are less well preserved. 



The greater number and more striking specimens belong apparently to a 

 species of Oreodon, larger than any previously discovered and equaling in size 

 Merycochcerus proprius. Indeed, so far as we are familiar with the skull of both, 

 the two are so nearly alike that one may be regarded as only a variety of the 

 other, or at most both may be viewed as distinct species of the same genus. 

 I am, however, disposed to view one as the offspring, by selection, of the 

 other, and regard them as corresponding species of two genera which existed 

 probably in different times or localities. 



The species, which I propose to distinguish under the name of Oreodon 

 suferbus, is indicated by a much mutilated skull, together with mutilated 

 crania, and portions of jaws with and without teeth, of half a dozen or more 

 individuals. The specimens indicate a little variation in the size of tin' ani- 

 mal, but it appears to have been on the average about the same as Meryco- 

 chcerus proprius. 



The form and constitution of the cranium are the same as in Oreodon Cul- 

 bertsoni, but large inflated ear capsules or tympanic bones exist as in Oreodon 

 major and 0. bullatus. 



The face is intermediate in character to that of Oreodon major and Meryco- 

 checrus proprius. It is rather more abruptly narrowed in advance of the orbits 

 than in the former, but not to the same degree as in the latter. The infra- 

 orbital arches are proportionately of much greater depth than in Oreodon ma- 

 jor, and the other species of the Mauvaises Terres of Dakota, but are not so 

 deep as in Merycochcerus proprius. Thus in Oreodon major it measures 9 lines 

 in depth, in 0. superbus 18 lines, in Merycochcerus proprius 23 lines. 



The orbits are comparatively small, as in all the family of the Oreodonts. 

 The lachrymal fossa is proportionately shallower than in 0. Culbertsoni and 

 0. major, and in this respect is more like that of 0. gracilis. 



The infra-orbital foramen in Oreodon superbus holds an intermediate posi- 

 tion to that of Merycochcerus proprius and that of the Mauvaises Terres 

 Oreodons. 



The jaws of 0. superbus appear not quite so robust proportionately as in 

 Merycochcerus proprius, and the bone of the lower jaw is of less thickness. 



The teeth of 0. superbus and Merycochcerus proprius agree in size and consti- 

 tution, but the premolars and canines of the former appear more compressed 

 laterally, or they are of less thickness from within outwardly, and are some- 

 what wider fore and aft. 



I am prepared to admit that all the characters by which I have attempted 

 to discriminate different species of Oreodon and Merycochezrus are not fixed, 

 but I nevertheless view them as sufficient to eliminate animals which would 

 be generally recognised as distinct. 



1870.] 



