408 Zoological Society. 



ternal appearance that may be noticed among its members, so that 

 we should anticipate but little difficulty in subdividing the order 

 into a number of natural groups, the confusion, and differences of 

 opinion that have existed, not only as to the manner in which the 

 order should be divided, but also as to the position which certain 

 forms should occupy, show sufficiently that the task is by no means 

 an easy one ; and when the structure of the diiFerent members of 

 the order is investigated, and those forms are known to us by which 

 the most strikingly different genera are blended one into another, it 

 becomes difficult to draw the lines of separation, and still more to 

 fix the characters by which the groups can with accuracy be distin- 

 guished from each other. In the present state of zoological science, 

 it seems scarcely worth while to allude to the distinction of planti- 

 grade and digitigrade, which though due to no less an authority than 

 Cuvier, can hardly be said to possess any claims to the title of a 

 philosophic distinction. Indeed the former of these divisions, if the 

 character be fully insisted on, will include a very incongruous assem- 

 blage of forms. 



It is upon the differences of the teeth that the subdivision of this 

 order has been made chiefly to depend ; but, although it does so 

 happen that in most cases the affinities of a species may be truly 

 predicated by the inspection of these organs, there are some in which 

 naturalists have been led into error by too rigidly depending on 

 them ; it must be recollected that, especially in an order like this, 

 where we find among the different species, every gradation between 

 a purely carnivorous diet, and the capability of subsisting entirely 

 on vegetables, the teeth, by the various degrees to which the differ- 

 ent cusps are developed, and also by the point at which the normal 

 development of true molars from behind may be arrested, present a 

 very great variet)'' in the amount of tubercular surfaces, or of tren- 

 chant edges, to suit the regimen of the species, without any neces- 

 sary connection with its true affinities. For instance, the remark- 

 able variation in the number of true molars presented by the different 

 genera of the Dog-tribe is known to naturalists ; and my own col- 

 lection possesses the skull of a small dog in which, such is the 

 arrest of development resulting from the shortening of the jaws, 

 that although the individual was very old, it had never developed 

 more than one true molar above and two below, or one behind the 

 carnassial tooth in each jaw, being one less than is usual in the 

 species. 



If we except the aberrant family of Seals, we find that this order 

 does not present so many of those very striking extremes of adaptive 

 modification as are to be met with in some others, the generally 

 lithe and active form prevailing through the order rendering a very 

 moderate amount of adaptive modification necessary to fit the animal 

 for almost any situation and mode of life, and from this cause it 

 also happens that since the fallacious nature of the old division into 

 plantigrade and digitigrade has been generally perceived, the classi- 

 fications of this order most usually adopted by naturalists have ap- 

 proached much nearer to those natural divisions, which the essential 



