^(library 



f 



THE OTTAWA NATURALIST ^*t > 



VOL. XXV. OTTAWA, MAY, 1911 No. 2 



ON ARCTOTHERIUM FROM THE PLEISTOCENE OF 



YUKON.* 



By Lawrence M. Lambe, F.G.S., F.R.S.C, 

 Vertetrate Palaeontologist, Geological Survey, Ottawa. 



A well preserved skull of the giant bear Arctotherium has 

 lately been acquired by the Geological Survey and is of interest 

 in many particulars. The specimen consists of the skull without 

 the lower jaw and was discovered at Gold-run Creek, Yukon, in 

 frozen Pleistocene deposits at a depth of forty feet beneath the 

 surface of the ground. 



This widely distributed but imperfectly known genus is 

 distinctive of the Pleistocene of the American continents. In 

 North America three species have been described, viz. : 

 A. pristinum (Leidy), from South Carolina; A. simum, Cope, 

 from California, and A. haplodon, Cope, from Pennsylvania. 

 The South American species, A. bonariense (P. Gervais) is from 

 the River Plata, Buenos Ayres. 



The discovery of the skull at Gold-run creek extends the 

 known range of the genus very much northward, as this is the 

 first record of the occurrence of Arctotherium in the northern 

 half of this continent. 



As indicated principally by the teeth, Arctotherium is 

 intermediate between the old-world Hyaenarctos and the genus 

 Ursus, and is notable for its great size which equalled, if it did 

 not exceed, the largest species of both these genera. 



The Yukon skull is remarkably broad in proportion to its 

 length and represents an individual of great physical power 

 and bulk. W 



It is in a good state of preservation, but has suffered injury 

 in the upper anterior portion, the nasals being absent with the 

 greater part of the forehead broken away. On the left side the 

 second incisor and the premolars in advance of the fourth have 

 fallen out and been lost, as have also the three incisors, the pre- 

 molars in front of the fourth, and the second* molar, of the right 

 side. Otherwise the specimen is perfect. 



* Communicated by permission of the Director of the Geological 

 Survey. 



