THALAECTOS 303 



anterior cusp than in U. arctos, its inner side more flattened, 

 giving the tooth a more carnassial appearance ; jjostero-internal 

 cusp relatively less developed. Large lower premolar essentially 

 as in U. arctos but with somewhat more slender cusp. Molars 

 differing from those of Ursus arctos in their smoother, less sculp- 

 tured crushing surface, and slightly more trenchant cusps. Form 

 of in^ not peculiar, though outer cusps are higher and narrower 

 and inner cusps relatively lower ; m'^ with inner cusps obsolete 

 and heel relatively narrower and less developed. Anterior lower 

 molar with metaconid and its accessory tubercle reduced to a low 

 irregularly tuberculate ridge ; commissure of protoconid and 

 paraconid obsolete ; hypoconid and entoconid smaller and much 

 nearer together than in Ursus arctos, though separated from 

 anterior cusps by a normally wide interval, in which, however, 

 there are no definitely formed accessory tubercles. Second lower 

 molar with the same elements as in U. arctos except for the 

 absence of all trace of an intermediary tubercle on inner side of 

 crown. Third lower molar with crown nearly flat, its margin 

 showing only the faintest trace of antero-internal and antero- 

 external elevations. 



Measurements. — Adult male from Behring Strait (mounted) : 

 head and body, 2670 ; tail, 90 ; hind foot, 370 ; ear, 80. For 

 cranial measurements see Table, p. 294. 



Specimens examined. — Nine, from the following localities : — Spitzbergen, 

 1 (U.S.N.M.); Griffin Bay, Wellington Channel, 1; Melville Island, 1; 

 Arctic Ocean, 1 ; no history, 5. 



[The Museum specimens appear all to have come from the 

 American side of the Atlantic] 



Family CANID^. 

 1821. Canidn: Gray, London Medical Repository, xv, p. 301, April 1, 1821. 



Geograpliical distribution. — Essentially cosmopolitan ; in E urope 

 west to Ireland. 



Characters. — Larger cheek-teeth of a combined trenchan t and 

 crushing type, the last upper premolar and first lower molar 

 strongly differentiated as carnassials, the former 3-rooted, its 

 inner lobe in front of middle of crown, its position, somewhat 

 posterior to level of anteorbital foramen, at point of greatest 

 mechanical etliciency ; auditory bulla moderately or considerably 

 inflated, without septum ; form rather light, the legs long ; size 

 moderate ; feet digitigrade ; toes, 5-4 or 4-4. 



RemarTcs. — Notwithstanding its wide distribution the family 

 Canidse is not rich in genera. About a dozen are now recognized, 

 three of which occur in Europe. 



