932 



incisors were in normal number 



TEETH. 



33 



q Q i 



whence 



the term Hexaprotodon proposed for this inter- 

 esting restoration by its discoverers, Cautley 

 and Falconer. 



I have before remarked that the even-toed 

 or artiodactyle Ungulata superadd the cha- 

 racters of simplified form and diminished size 

 to the more important and constant one of 

 vertical succession in their premolars. These 

 teeth in the Ruminants, e. g. (Jig. 580., VII., 

 Mosciius,/). 2, 3, 4), represent only the moiety 

 of the true molars, or one of the two semi-cylin- 

 drical lobes of which those teeth consist, with 

 at most a rudiment of the second lobe, as 

 Cuvier very accurately describes*, and F. 

 Cuvier figures in pi 94. of his useful work, 

 " Dents des Mammiferes." An analogous 

 morphological character of the premolars will 

 be found to distinguish them in the dentition of 

 the genus Sus (figured in my " Odontography," 

 pi. I40.,jigs. 1 and 2), in the Hippopotamus (ib. 

 pi. 143.), and in the Phacochcerus (ib. pi. 141.), 

 where the premolar series is greatly reduced 

 in number : yet this instance of a natural 

 affinity manifested in so many other parts of 

 the organisation of the artiodactyle genera has 

 been overlooked in F. Cuvier's work above 

 cited, although it is expressly designed to 

 show how such zoological relations are illus- 

 trated by the teeth. Confiding in the accuracy 

 of the Baron Cuvier's division of the hoofed 

 quadrupeds into " Pachyderms " and " Rumi- 

 nants," M. F. Cuvier separates the non ru- 

 minant Artiodactyles from the ruminant ge- 

 nera of the same natural division by interposing 

 the Tapir, Hyrax, Rhinoceros and Elephant ; 

 whilst the horse, which, in the size and com- 

 plexity of its premolars, as well as in many 

 other characters, arees closely with the other 

 perissodactyle Pachyderms, is placed in close 

 juxtaposition with the Ruminants.-}* 



Most of the deciduous molars of the Rumi- 

 nants resemble in form the true molars ; the 

 last, e.g. (fig. 593., d. 4), has three lobes in the 

 ower jaw J like the last true molar (m. 3.). They 



Fig. 593. 



di 



Permanent and deciduous teeth, Sheep (Ovis). 

 (Lower jaw.~) 



are three in number on each side, and, being 

 succeeded by as many premolars, the ordinary 



permanent molar formula is . _ ni ^ . 

 r 33' ' 33 ' 



* Ossemens Fossiles, 4to, torn. iv. p. 6. 



f See my " Remarks on the Classification of the 

 Hoofed Quadrupeds " in " Quarterly Journal of the 

 Geological Society," May, 1848. 



% When, therefore, the third grinder of the lower 

 jaw of any new or rare Ruminant shows three lobes 

 the crowns of the premolars should be sought for 

 in the substance of the jaw below these, and above 



but there is a rudiment of d. 1 in the embryo 

 fallow-deer, and in one of the most ancient of 

 the extinct Ruminants (Dorcatherium, Kaup) 

 the normal number of premolars was fully de- 

 veloped. 



Sufficient, it is hoped, has been adduced to 

 prove that the molar series of the Diphyo- 

 donts is naturally divisible into only two 

 groups, premolars and molars ; that the ty- 

 pical number of these is ~ and that 



'r 4> o O 



each individual tooth may be determined and 

 symbolised throughout the series, as is shown 

 in the instances under cut 580. If anything 

 were wanting to prove the artificial character 

 of a three-fold division of these teeth, and the 

 futility of any other classification than that 

 founded upon development, it would be af- 

 forded by the attempt to determine the homo- 

 logous teeth which is exemplified by the 

 dotted line which traverses the series, and 

 which crosses the teeth distinguished by the 

 name "principales" in the great " Osteo- 

 graphie and Odontographie " now in course 

 of publication by Prof, de Blainville. 



This author abandons the classification of 

 the molar series adopted by the Cuviers, 

 without assigning his objections to it ; and 

 proposes another, in which he divides the 

 series into " avant-molaires, principalesr *md 

 arriere-molaires ; " he exemplifies this division 

 by the human dentition, in which the five 

 grinders on each side of both jaws are for- 

 mulised as " deux avant-molaires, une princi- 

 pale, et deux arriere-molaires."* 



With regard to the characters of these 

 kinds of teeth, the avant-molaires are " simple 

 or complex," the principale is " trenchant," 

 and the arriere-molaires are " tuberculous." f 

 But as shape is not a constant character, 

 especially in the "principale," the author pro- 

 poses another from its position, describing 

 it as " being implanted below the root of 

 the zygomatic process of the maxUary bone * 

 in the upper jaw ; and stating that the tooth 

 which opposes it below, and is in advance 

 of it, or crosses in front of it, is the lower 

 " principale." 



In defining the dentition of the genus Felis J, 

 M. de Blainville accordingly assigns 1 " avant- 

 molaire," 1 " principale," and 2 " arriere- 

 molaires " in the upper jaw ; and 1 " avaut- 

 rnpUure," 1 " principale," and 1 " arriere-mo- 

 laire " in the lower jaw. In another part of 

 the same work , he, however, proposes another 

 formula, viz., 2 " avant-molaires," 1 " princi- 

 pale," and 1 " arriere-molaire " above ; 1 

 " avant-molaire," 1 " principale," and 1 " ar- 

 riere-molaire " below; but, taking either of 

 these determinations, or the dental formulae 

 which he assigns to other carnivorous genera, 

 and comparing them with his formula of the 



their opponents in the upper jaw; and thus the 

 true characters of the permanent dentition may be 

 ascertained. 



* Oste'ographie, torn. i. p. 43. 



t Ib. p. 43. 



1 Oste'ographie des Carnivores, p. 69, 



Osteographie des Felis, p. 55. 



