380 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



The iutercolumnar tubercles are small, and are only present in the true 

 molar teeth. The molars are about half- worn 5 at this stage, the anterior 

 lake of the three last, communicate with the median inner vertical fis- 

 sure, by their posterior horn. 



AUCHENIA VITAKERIANA, sp. tlOV. 



This llama is represented by a portion of the left maxillary bone sup- 

 porting molar teeth, which was found in a Pliocene deposit in Oregon, 

 in association with two larger species of the genus, the A. hesterna 

 and the A. major {PalaucJienia Owen). Its size is less than those at- 

 tained by the two species named, but exceeds considerably that of A. 

 lama of the Andes. The details of the structure of the first and second 

 true molars are quite similar to those of the existing species. The last 

 premolar is broken away, but its roots show that its size was consider- 

 able, lacking little in antero-posterior diameter that of the first molar. 

 The base of the first (or third) premolar is very small. It possessed 

 either but one small root, or possibly two, the second being represented 

 by a small fossa on the inner side of the anterior root of the last pre- 

 molar, of doubtful significance. The palatal foramen is opposite the 

 line of contact of the two premolars, instead of anterior to the first, as 

 in A. lama. The infraorbital foramen is over the line of contact of the 

 last premolar and first true molars. 



Measurements. 



M. 



Leug th of bases of molar series, the last one omitted 0.069 



Length of crown of first true molar - 0.024 



Width of crown of first true molar 0.014 



Length of base of last premolar , , 0.020 



Width of palate at first true molar • 0.042 



This species is dedicated to Governor John Whitaker, of Oregon, who 

 discovered the locality froin which this fossil was obtained. The forma- 

 tion is Pliocene. 



TiCHOLEPTUS ZYGOMATICUS, 0671. et Sp. flOV. 



Char. gen. — This genus is known from cranial characters only. Den- 

 tal formula, I. f ; 0. i ; Pm. A ; M. |. Teeth in general similar to those 

 of Oreodon; the true molars with short crowns ; the first inferior pre- 

 molar the functional canine. Premaxillary bones consolidated into a 

 single mass ; symphysis not co-ossified. A preorbital fossa, and a large 

 foramen in front of it, bounding the maxillary bone superiorly and 

 posteriorly. No vacuities between the orbits. 



This genus of Oreodontidw occupies an interesting position between 

 the three prominent forms of the family, Oreodon, Merycochoerus, and 

 Leptauchenia. It combines the dentition and preorbital fossa of the first 

 with the solid premaxillary of the second and the large facial vacuities 

 of the third. 



Char, specif. — The T.zygomaticus is only known from the cranium of 



