NATURAL SCIENCES OF PHILADELPHIA. 191 



July 4, 1871. 

 Mr. Mactier in the chair. 

 Eight members present. 



ReynarlcH on Donation of Fossils from Wyoming. — Prof. Leidy 

 directed attention to the collection of fossils presented this evening 

 b}^ Dr. JosejDh K. Corson, stationed at Fort Bridger, Wyoming 

 Territory. The fossils, consisting of remains of mammals, tnrtles, 

 and crocodiles, were obtained at Grizzly Buttes, in the vicinity of 

 Fort Bridger. Among the mammalian fossils are many pertaining 

 to Palseosyops paludosus, consisting of portions of the skull, jaws 

 with and without teeth, articular extremities of the limb bones, 

 etc. Dr. J. Van A. Carter had recently sent to Prof. Leid}- some 

 well-preserved portions of jaws with teeth, of the same animal, from 

 Lodge-pole-trail, thirteen miles from Fort Bridger, and also from 

 Heniy's Fork of Green River. Among the specimens from the 

 latter localit}^, there is the most complete series of the upper molar 

 teeth which he had yet seen. 



The specimens of jaws and teeth indicate a variation in the size 

 of Palseosyops. The molar series of teeth further undergo a 

 rapid reduction in size fi'om behind forwards, so that from isolated 

 specimens of teeth, the smaller anterior molars might readilj- be 

 viewed as pertaining to a smaller species. Prof. Marsh had 

 recently designated what he supposed to be a smaller species of 

 Palseosyops with the name of P. minor., from an inferior molar 

 tooth, "apparently from near the middle of the series." The 

 measurements which he gives to the tooth, ten lines fore and aft, 

 and five lines in front, and five and sixteenths behind, at the 

 summit of the lobes, would apply to the first true molar of P. 

 paludosus., while the last premolar is still smaller. 



In a nearly complete ramus of the lower jaw of P. paludosus., a 

 series of teeth, consisting of the true molars and the two pre- 

 molars in advance, measures G4 lines. Another series of true 

 molars measures 46 lines. These measure in succession fore and 

 aft, 11 lines, 15 lines, and 19 lines. The last premolar, looking 

 like a reduced molar with the hinder lobe proportionately less 

 well developed, measures scarcely 9 lines. 



1871.] 



