216 T7HSID-E. 



lu the 'Annals of Philosophy' for 1825, I divided the Bears into 

 groups, according to the characters of their feet and claws, and into 

 the genera Ursus, Banis, Prochilus, and TlutJassarctos. 



The examination of the series of sknlls of Bears in the Museum, 

 like the examination of the series of bones of the Yiveiridae, has 

 strongly impressed me with the uncertainty that must alwaj'S attend 

 the determination of fossil bones, or indeed of bones of all animals 

 when we have only the skulls or other bones of the body to com- 

 pare with one another. There can be no doubt that the study and 

 comparison of the bones of the different species is very important 

 — that the skull and teeth aiford some of the best characters for 

 the distinction of the genera and species ; but few zoologists and 

 palaeontologists have made sufficient allowance for the variations 

 that the bones of the same species assume. In the Bears I have 

 observed that there is often more difference between the skulls of 

 Bears of the same species from the same locality than between the 

 skulls of two undoubted species from very different habitats and 

 with very different habits. Thus I have the skulls of some Bears, 

 the habitat of which is not certainly known, which I have doubts 

 whether they should be referred to the Thibet Bear {U. iorq^tatus) 

 or to the North-American species ( U. americanus) ; but I have re- 

 ferred them to the latter with doubt, as they were said to have come 

 from the latter country. It is the same with regard to the skull 

 of a Bear that lived in the Zoological Gardens for years, which has 

 the general form of the skull and the wide palate of the European 

 Bear, but the long last grinder and some other characters of the 

 Ursus ferox. 



This similarity of the skull is more remarkable, as no two Bears 

 can be more distinct from each other than the species above named 

 which have such similar skulls, showing that similar skulls do not 

 always imply very nearly allied or doubtfully distinct species. 



The Bears may be arranged, by the size of the tubercular grinders, 

 thus : — 



Very large, more than half as long again as the flesh-tooth. (The 

 number gives the medium measurement of the flesh-tooth, in inches 

 and twelfths.) 1" 4'", Ursus isabeUiiiKS. 1" 5'", U. cinereus. 1". 4'", 

 U. grandis. 1" 3'", U. torqiiatus. 



Moderate, above half as long again as the flesh-tooth. Thalas- 

 sarctos maritimus. 1" 2'", Ursus arctos. 1", U. arhoreus. 1", U. 

 americanus. 1" 6'", 3Ii/rma7-ctos. 



Small, only rather larger than the flesh-tooth. Helarctos mcday- 

 anus, Melursus libycus. 



