CLASSIFICATION. MAMMALIA.- 



JLASSIFICATION. 



We have not thought it necessary to indicate in the 

 history of the classification of the Mammalia, the differ- 

 ent steps by which Cuvier's arrangement has been 

 modified so as to produce the fourteen orders shortly 

 characterized above. These consist in the separation of 

 the Cheiroptera, Insectivora, and Pinnipedia, from the 

 Carnassiers of the great French zoologist ; in the sepa- 

 ration of the horses from the Pachydennata of Cuvier, 

 to form the order Solidungula, and in the establish- 

 ment of the order Monotremata for the edentulous 

 aplacental mammals, placed by Cuvier and some other 

 authors with the Edentata. 



In concluding this portion of our subject we must 

 devote a little space to the consideration of a new 

 scheme of classification of the Mammalia lately put 

 forward by the distinguished British comparative anato- 

 mist, Professor Owen. Starting from the assumption 

 that the brain, as the centre of the nervous system, the 

 most important of all the constituent elements of the 

 animal body, must necessarily be modified in accord- 

 ance with the habits, instincts, and powers of the various 

 creatures, Professor Owen has taken the structure of this 

 wonderful organ as the foundation of his system ; and 

 from the characters thus obtained he concludes that the 

 two subclasses of placental and nonplacental mammals 

 are not of equal value, and that it would be more proper 

 to divide the class into four subclasses. Of these the 

 first, which Professor Owen denominates the LYENCE- 

 PHALA, or " loosed-brained," are distinguished by the 

 imperfect union of the two cerebral hemispheres, from 

 the want of the corpus callosum already referred to ; 

 the hemispheres are smooth and small, exposing the 



olfactory and optic lobes and the cerebellum. This 

 subclass corresponds with our Aplacentalia. 



In a second subclass the hemispheres of the brain are 

 united by a corpus callosum, but are not much lareer 

 than in the preceding, leaving the greater part of the 

 olfactory lobes and the cerebellum exposed; their surface 

 is slightly convoluted in a few of the largest species of 

 the group, but in the majority they are smooth. From 

 this circumstance Professor Owen proposes to call the 

 animals of this subclass LISSEXCEPHALA. 



Those of the third group have the surface of the 

 brain more or less convoluted, with but very few ex- 

 ceptions. Hence they are called GYRENCEPHALA. 

 The cerebral hemispheres are much more largely 

 developed in this than in the two preceding groups, 

 and cover more or less of the cerebellum and olfactory 

 lobes. 



Lastly, in the highest subclass, the ARCHENCEPUALA, 

 which includes only the human species, we find nearly 

 the same cerebral characters as in the third group ; but 

 the hemispheres are much larger, forming the whole 

 mass of the brain when viewed from above, and the 

 convolutions are deeper and more numerous. 



The animals belonging to each of these subclasses 

 present certain anatomical peculiarities in common, 

 which are carefully indicated by Professor Owen in his 

 paper, and appear to lend considerable support to his 

 views. The orders admitted by the learned professor 

 are for the most part identical with those adopted in 

 the present work ; the differences in this respect and 

 in the general arrangement will be easily seen from the 

 following table : 



PROFESSOR OWEN'S CLASSIFICATION OF MAMMALIA. 



SUBCLASSES. OEDEBS. 



Archencephala, BIMANA. 



:;;;;. 



Gyrencephala, , { Ungulata, . 



j^Mutilata, .. 



Lissencepliala, 



Lyencephala, 



f ARTIODACTYLA. 

 I PERISSODACTYLA. 

 j PROBOSCIDIA. 



TOXODONTIA (fosSU). 

 SlRENIA. 



CETACEA. 



BRDTA. 



CHEIROPTERA. 



INSECTIVORA. 



RODENTIA. 



MARSUPIALIA. 



MOXOTREMATA. 



The Pinnipedia (seals) have vanished from the list to 

 take their old place amongst the Carnivora, and the Soli- 

 dungula no longer figure as a distinct order ; but these 

 losses are compensated by the division of the Cetacea 

 into two orders, and by the establishment of the order 

 Proboscidia for the elephants. The principal difference, 

 besides these, between the classification proposed by 

 Professor Owen and that adopted by the present writer 

 consists in the mode of division of the rest of the hoofed 

 quadrupeds. These, with Professor Owen, form the two 

 orders Artiodactyla and Perissodactyla, or even-toed 

 and odd-toed beasts the former including the ruminants, 

 the pigs, and the Hippopotamus ; the latter the horses, 

 the tapirs, the Hyrax, and the rhinoceroses. It seems 

 to the author, however, that this mode of arrangement, 

 the principal merit of which consists in its allowing 

 the assignment of a definite place in the system to 



the remains of certain extinct species of Mammals, can 

 hardly be regarded as natural when applied to those 

 creatures, the whole of whose organization is known 

 to us. The Ruminants appear to constitute a most 

 natural and well-defined group, which cannot, taking 

 the mass of their characters into consideration, be 

 properly associated in the same order with any other 

 forms of quadrupeds ; so that the only course to be 

 adopted would be that of establishing a separate order 

 for the pigs and Hippopotami. This, however, doe? 

 not appear to us to be necessary, and we shall therefore 

 adhere in the present work to the old orders, Rumi- 

 nantia and Pachydennata. 



As regards the general arrangement or sequence of 

 the orders and the establishment of the subclasses pro- 

 posed by Professor Owen, no one can venture to give 

 an opinion who has not thoroughly and patiently worked 



