184 Professor Owerij on the [Jan. 27, 



greater number and mobility of the digits and the smaller extent to 

 which they are covered by horny matter. This substance forms a 

 single plate, in the shape of a claw or nail, which is applied to only one 

 of the surfaces of the extremity of the digit, leaving the other, usually 

 the lower, surface possessed of its tactile faculty. 



All the species are ' diphyodont/* and the teeth have a simple 

 investment of enamel. 



The first order, Carnivora, includes the beasts of prey, properly 

 so called. With the exception of a few Seals the incisors are 



Q Q -j -J 



■X — 5 in number ; the canines ^^ — r, always longer than the other teeth, 



and usually exhibiting a full and perfect development as lethal 

 weapons ; the molars graduate from a trenchant to a tuberculate form, 

 in proportion as the diet deviates from one strictly of flesh, to one of a 

 more miscellaneous kind. The clavicle is rudimental or absent ; the 

 innermost digit is often rudimental or absent ; they have no vesiculae 

 seminales ; the teats are abdominal ; the placenta is zonular. 



The Carnivora are divided, according to modifications of the limbs, 

 into * pinnigrade,' * plantigrade,' and * digitigrade ' tribes. In the 

 Pinnigrades (Walrus, Seal-tribe) both fore and hind feet are short, and 

 expanded into broad, webbed paddles for swimming, the hinder ones 

 being fettered by continuation of integument to the tail. In the 

 Plantigrades (Bear-tribe) the whole or nearly the whole of the hind 

 foot forms a sole, and rests on the ground. In the Digitigrades (Cat- 

 tribe, Dog-tribe, &c.) only the toes touch the ground, the heel being 

 much raised. 



The principle of the more specialized character of actual organisa- 

 tions receives illustration in the genetic history of the present order. 



The genera I^elis and Machairodus, with their curtailed and other- 

 wise modified dentition and their strong short jaws, become, thereby, 

 more powerfully and effectively destructive than the eocene Hycenodons 

 and miocene Pterodons, with their numerically typical dentition and 

 their three carnassial teeth on each side of the concomitantly prolonged 

 jaws, could have been. 



In the most strictly carnivorous Gtrencepeala the paw is per- 

 fected as an instrument for retaining and lacerating a struggling prey 

 by the superadded elastic structures for retracting the claws and main- 

 taining them sharp. We next find in the unguiculate limb such a 

 modification in the size, shape, position, and direction of the innermost 

 digit that it can be opposed, as a thumb, to the other digits, thus con- 

 stituting what is properly termed a ' hand.' Those Unguiculates which 

 have both fore and hind limbs so modified, form the order Quad- 



2 o 1 "1 3 3 



HUMANA. Most of them have ^ — jz incisors, -i — ~ canines, 5 — - broad 



A — Z JL — 1 o — o 



tuberculate molars, and premolars in variable numbers ; all have per- 



♦ See Philosophical Transactions, 1850, p. 493 ; and Art. * Odontology,' Encycl. 

 Britannica, 1858. 



