lOS MAMMALIA. 



cossfullv attiick tlie lianlest substanoes, fixMiuciitlv frcilmj,' on \vooil and the Ijark of trees. 

 The Ijetter to accorajilish tliis object, tliese incisors have enamel only in front, so that 

 tlieir posterior edges wearing aiiay faster than the anterior, they are always naturally slo])e(l 

 [or chisel-like]. Their prismatic form causes them to grow from the root as fast as they wear 

 away at the tip [their formative pul])s being persistent] ; and this tendency to increase in 

 length is so powerful, that if either of them be lost or broken, its antagonist in the (jtlier jau', 

 having nothing to oppose or comminute, becomes de\elo|)ed to a monstrous extent.* The 

 mh-rior jaw is articulated by a longitudinal condyle, in such a wav as to alhjw of no horizontal 

 mi/tion, e.\eept from back to front, and vice versa, as is reciuisite for the action of gnawing. 

 The molars also have fiat crowns, the enamelled eminences of which are always transversal, so 

 as to be m 0]iposition to the horizontal movement of the jaw, and better to assist in 

 ti-ituration. 



The genera in which these eniincnees are sinijile lines, and the crown is verv flat, are more 

 exclusively frugivorons ; those in whi(di the eminences of the teeth are divided into Idunt 

 tubercles are f)inni\oroiis ; while the small luindier of such as ha\'e no |)Oints more readily 

 attack other animals, and ap]n-oximate somewhat to the CaniarUi. 



The form of the body in the Rndeiitio is generally such, that the hinder jiarts of it exceed 

 those of the front ; so that [with the exception of a large South Anieriean group, including 

 the (iuinea-pig ami its allies,] they rather leap than run. In some of them, this ihsproportion 

 is even as excessive as in the Kangaroos. 



The intestines of the Roiiciifia are \"erv long; their stomach simple, or but little divided; 

 find their ca'cuni often A"ery ^'oluunnous. even more so than the stomach. In the subgenus 

 Uli/nxus, however, this intestine is wanting. 



Throughout the present group, the brain is almost smooth and without furrows ; the orbits 

 are never separated from tlie temporid fosstef, which have but little depth: the eyes are 

 directed siilew ays : the zygomatic arches, thin and curved below , announce the feebleiicss of 

 the jaws; and the fore-arms have almost lost the ]iow"er of rotation, their two Ijones being 

 often united : in a word, the inferiority of these animals is perceptiljle in most of the details 

 of their organization. Those genera, how e\'er, w hieli have stronger claMcles, displa;" a certain 

 dcL'ree of address, and employ their fore-feet together to hold u)) food to the mouth ; some of 

 them even climb trees with facility. 



[ffc have seen that in the true Lemurs the middle superior incisors are separated by a wide 

 interval, which in the Cohigos (iiiileiipillieeus] is still more extended: in Projiitlieciis of 

 Mr. Bennett, on the contrary, the front pair are brought nearly contiguous, having more of 

 the Monkey character than in other Slrr'iislrrhiiii. The lower canines also, which are directed 

 horizontallv forward throughout that grniip. and ;ip[ii(ixini;ited so as to leave little room for 

 the intervening incisors, which are accordingly extremely narrow or eoiu])ressed, are even 

 more approximated in the Propithecus, so that one jiair of the incisors is necessarily saeri- 

 tii-ed ; ;iuil hence the diiiiinntinii of the interspace between the upper incisors. Now iu 

 tins we may discern a slight ap]iroaeli to the rodent character of Cliriroiiii/s, in the loss of one 

 p;iir of incisors. In the latter genus, the whole of the incisors disap|iear, the canines of both 

 jai\s occupying their site : precisely as in the true Rmlentiii, wherein also the incisors and not 

 the canines or tusks are almost without execiition obliterated, as is beautifully shown in the 

 instance of the Hare, i\liere true incisors exist jiosterior to the upper gnawing teeth : it will 

 be obsciTcd that in all Rodentia the eurreiitly reputed incisors j)ass through the uiter- 

 m:i\iliaries ; whih' the constant hmitiition of their number to two in each j.aw, and the inva- 

 riable absence of any trace of other teeth in the ordinary positi(ni of canines, assist in ecui- 

 tirming the opinion here decidedly entertained rcsjiecting the nature of what h;rve l)cen desig- 

 nated incisive teeth in these animals. It may be added that the Ularsupiata do not, therefore, as 



tlms pr<j]ornjp(l. and I t They art su in C/iciruwi^j, ranged by the author in this order.- 

 claHal.— Eo. I Ed. 



