140 MAMMALIA— DENTITION OF MAMMALS. 



ever, from within the true maxillaries— or they are directed outwards, as in the Pigs and Hippopotami. Tlie 

 composite structure of the molars, from which this order takes its name, attains its most remarlvable develope- 

 ment in the present division, as obser\'ed in the Elepliant, the Capybara, and the Phascochoere. They have rarely 

 fewer than four, and often five distinct toes on each foot ; and generally a cleft upper lip, less observable when the 

 nose is prolonged into a snout, or proboscis. They separate into Proboscidia, Rodentia, C/iarodia, and Syrenia. 



The close affinity of the Proboscidia and Rodeniia was distinctly pointed out and descanted upon by Cuvier in 

 his Ossements Fossiles, to which valuable work the reader is necessarily refeired, from want of space to enlai'ge 

 upon the subject here. The tusks of the Proboscidia are mostly peculiar to the upper jaw, where they attain 

 enormous dimensions, being small when present in the lower one. Their form is cylindrical, with conicaJly- 

 pointed tips, and they are surrounded with enamel.* 



The Rodentia have approximated tusks in both jaws, with enamel only in front ; and the Hares alone among 

 them possess true incisors in the upper jaw only, in front of which the tusks pass, protruding in their usual site 

 throughout the group. They have neither an elongated snout nor a proboscis ; and their extremities are unguicu- 

 lated. In the Hare, which has six rootless molars, the three first alone are preceded by rooted milk teeth ; and 

 the anterior molao in numerous other genera, the adults of which have four, is in like manner preceded by a 

 deciduous rooted tooth, which is shed about the time the last posterior molar protrudes through the gum. 



The Cha'rodia have always incisors, their tusks, of similar kind to those of the two preceding groups, being 

 directed outwards, and those of the upper and lower jaws generally rubbing against each other. The Swine and 

 Hippopotami are characteristic examples ; and we are disposed to refer to this division (as a distinct minor group), 

 the very singular genus Hyrax, the adults of which do not possess canines. 



Lastly, the Syrenia, or Cetacea herbivora, Cuv., which have no posterior extremities, like the Isodontia, are 

 likewise deprived of canines, at least the existing genera; for the iJ^ino/Aerawi (assuming that this lost genus is 

 correctly placed here) had enormous tusks in the lower jaw only, anomalously turned downward. Their general 

 anatomy leaves no doubt of the propriety of separating them altogether from the Isodontia, or zoophagous 

 Cclorea, and allies them (we consider) most nearly to the Charodia. 

 The Ungnlata, or grazing animals, divide, according to the simple or complex stomach, into Belhia & Riiminantia. 

 The Bellua consist of the Horses, Tapirs, Rhinoceroses, and proximate fossil genera ; all of which now existing 

 have a prehensile upper lip more or less developed, the nostrils being prolonged with it into a short flexible pro- 

 boscis in the Tapirs, and there is reason to conclude in many of the extinct forms. The true and false molars 

 present no sensible ditference in the adult animal ; but the dentition of the young proves that the normal comple- 

 ment of true molars is not exceeded. 



The Riiminantia fall into Ancerata and Pecora ; the fonner consisting of the Camels and Llamas, which have a 

 cleft and prehensile upper lip, and claw-like hoofs upon which they do not rest; and the latter of the remainder, 

 which have the upper lip entire and non-prehensile, (the tongue becoming so in its stead,) and the ends of their 

 toes encased in hoofs, upon the soles of which the weight of the body is supported. The former alone possess any 

 superior incisors, though only one pair ; but all have six incisors in the lower jaw, together with inferior canines, 

 which in the Pecora assume the form and direction of incisors, but the true analogy of which appears on com 

 j)arison of them with the lower canines of either the Bellua or Ancerata, and of the Bactrian or Two-humped 

 Camel in particular, which has no interspace (as in the others) between its lower canines and incisors. 



The APLonoNTi A, or abnormal division of the phytophagous type, corresponding to the Edentata of Cuvier, is 

 now in course of becoming unexpectedly elucidated by the extraordinarily rapid discovery of fossil genera in South 

 America, which present a more complicated form of molar tooth than was previously known m this division, as 

 exemplified by the newly established genera Mylodon, Glyptodon, and we venture to suggest — Toxodon, 

 wherein the indentations of the enamelled sides of the teeth resemble those of many rodents. However numerous 

 may be the false molars in certain genera of this division, the number of their true molars appears in no instance 

 to exceed three, (at least in those which we have been able to examine, comprehending all with the unfortunate 

 exception of Priodon) ; and the structural distinction between their true and false molars is sufficiently evident. 



Of the two Ovo-viviparous orders, there is only space left to remark, that whereas the Placental Carnivora and 

 Herbivora are (as we have seen) modified upon two distinct types, which do not pass into each other, the Marsu- 

 \na.\'Carnivnra and Herbivora pertain to the same equivalent type, and grade into each other so that an analogous 

 line of rigid demarcation cannot be traced. This perhaps may be added to the various indications of their 

 nhnorinity as a group, as compared with the preceding or Placental subclass of Mammalia. 



In conclusion, it may here be noticed, that without intending any thing of the kind while gradually ascending 

 to the foregoing classification, it has so happened that species with superior intelligence in conformity with their 

 cerebral devclopeinent are placed at the head of each principal group, which may or may not be fortuitous coinci- 

 dence. Thus, ISLin ranks at the head of the most highly organized order— Ty/iodontia, the Dolphin at the head of 

 the Isodontia, and the Elephant at that of the great phytophagous division, and, consefjuently, of the Uijdodnntia ; 

 while the Dog ranges first among the Seciindatcs, and the Horse first of the I'ngutata. The leading genus of the 

 Apliidontia may yet remain to be discovered. The animals here mentioned (at least the terrene kinds, for of the 

 Dolphin we do not possess the requisite data for forming an opinion), certainly appear to possess more eminently 

 culfurable intellects than any others, such as may be applied to purposes having no relation to their natural 

 habits ; and Man has accordingly been enabled to gain them as assistants in his various labours and occupations.] 



* II may he thiit the Prnbntrldin supply an exception to the other- 

 wise uiiivcrsnl rule of jilacental Mnmmulin liiiviriK never more than 

 three pairs of true molar« in cither jaw; but we suspect that such 

 vceiniMK exception would upon analysis pruve In be more apparent than 



real, tlie last of them beinR probably aiialoi^oua to the teeth wlii''h 

 human beings sometimes develope when in vigorous senility ; theoreti 

 cally, a renewal of their predeeessors. 



