222 



Flat," has the appearance in condition of i)reservation, color, and wear, as if 

 it might have pertained to the same individual as the former specimen. If 

 so, it is related to it apparent!}' as the last premolar to the first molar. The 

 antero-posterior diameter of the crown is nearly 16 lines; the transverse 

 diameter is 19 lines. The basal ridge and inner lobes are as in the former 

 tooth. Traces at the bottom of the oblique valley appear to indicate a dispo- 

 sition to the formation of two folds like those existing in the same position in 

 the larger tooth. 



It is not unlikely that this second molar tooth may be a true molar of the 

 preceding species. 



The crown of a lower molar tooth, represented in Figs. 24, 25, Plate VII, 

 from Bridge Creek, is supposed to belong to R. imcificus. It measures 20 

 lines fore and aft, and 1 inch transversely, at base. 



HADROHYUS. 



Hadrohyus supremus. 



Among the Condon collection of Oregon fossils there are several, apparently 

 of a large pachyderm, differing from those previously indicated, and likewise 

 different in character from such as have been heretofore described. 



Fig. 26, Plate XVII, represents a fragment of a tooth which I have sup- 

 posed to be a last upper premolar. The crown of the tooth would appear in 

 its entire condition to have nearly the form and construction of the corre- 

 sponding tooth of the Oreodonts, but differs especially in the proportionately 

 less degree of development of the inner lobe and the greater degree of pro- 

 duction of the inner basal ridge. The remains of the inner lobe have the 

 appearance of being composed of a nearly connate pair, which no doubt 

 would be found better developed and more distinct in the succeeding teeth. 

 In the specimen the inner lobe appears notched, and the dentine is exposed 

 on the outer lobe and the anterior division of the inner lobe. 



The transverse diameter of the specimen is 1^ inches. The tooth is 

 labeled "Alkali Flats," and may be regarded as representing the animal to 

 which the above name is given. 



Another specimen pertaining to an animal as large as that to which the 

 tooth just described belonged, and perhaps actually belonging to the same, 

 consists of a brain-cast, or rather the cast of the interior of a cranium. The 

 cast has nearly the size and shape of the brain of a horse. The cerebral 



