VERTEBRATE REMAINS, PORT KENNEDY BONE DEPOSIT. 221 



sectional part of the first inferior true molar. This is due to the more anteropos- 

 terior direction of the paraconid. the larger size of the protoeonid. and the smaller 

 size of the metaconid. The tooth makes a sensible approach to that of Hyaenarctos. 

 To this group belong the following species, and they differ in the following ways : — 



I. Superior premolars crowded, overlapping. (South American.) 



Large species; JJ. ornatus Cuv.. U. boucerensis Gerv. 



Smaller species ; U. brasiliensis Linn. 



II. Superior premolars uninterrupted, not overlapping. (California!].) 



Muzzle very short ; JJ. simus Cope. 



III. Superior premolars spaced. (E. N. America.) 



Muzzle moderate ; U. Jiaplodon Cope. 



Where U. pristinus should be placed in this series can only be ascertained by 

 future discovery. The first named three species are separated from Ursus under 

 the name of Tremardos Gerv. (Arctotherucm Brav.), as the humerus exhibits an 

 entepicondylar foramen. It is not known whether the last two species possess this 

 character or not. 



A conspicuous character is common to Tremardos ornatus and Ursus {? Tre- 

 mardos) Jiaplodon. which is not present in Tremardos boncerensis of the Pampean 

 beds. There are two masseteric fossa? of the mandible, which are separated by a 

 crest which extends obliquely downward and backward from below the coronoid 

 process. 



The size of the teeth of this species as well as that of the jaws preserved, 

 exceeds the average dimensions of the grizzly bear {Ursus liorribilis). U. Jiaplodon 

 was evidently one of the most formidable of its genus, and it probably found an 

 abundant supply of food in the sloths of the genus Megalonyx. which were the most 

 abundant of the contemporary mammalia. 



I take as the typical specimen that in which both jaws are present, although 

 several others exhibit the characters of special teeth more perfectly. The incisive 

 part of the premaxillary bone is wanting. The inferior and part of the anterior 

 orbital border is preserved, and also the coronoid process and condyle of the mandi- 

 ble. Of the superior dental series are preserved the c, pm. 1-3—1, m. 1-2. Of the 

 inferior series there remain pm. 3-4, m. 1-2-3. The external face of the ramus 

 from the base of the coronoid process to the angular region is broken away. 



The proportions of the muzzle are shorter and deeper than in the living ursi, 

 but they are not so short and deep as in U. simus 1 of the California caves. The 

 length measured horizontally from the inferior border of the orbit in line with the 

 anterior border to the premaxillary border is to the depth to the alveolar edge of 

 the maxillary bone, from the same point, as 9 to 7. In U. simus these proportions 

 are as 8 to 9. The characters of the infraorbital foramen can not be determined, 

 owing to injury to the specimen. A conspicuous feature of the lower jaw is the 

 large fossate form of the ramus anterior to the masseteric fossa, as far forward as 



1 American Naturalist, 1891, p. 998. Plate XXI. 



