Classification. MASIMALIA. Classification. 
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 Pachydermata 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 larger 
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 Lissencephala. 
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 Archencephala, 
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 : — 
SUBCLASSEB. 
Arcliencephala, 
Gyrencephala, . 
Lissencephala, . , 
Lyencephala, . . . 
professor Owen’s classification of siammalia. 
Unguiculata, 
j Ungulata, 
Mutilata, 
Bimana. 
r Quadrumaka. 
t Carnivora. 
r Artiodactyla, 
J Perissodactyla. 
j Proboscidia. 
GPoxodontia {fossU]. 
_f Sirenia. 
t Cetacea. 
f Bruta. 
J Cheiroptera. 
1 Insectivora. 
[_ Rodextia. 
I Marsupialia. 
( Monotremata. 
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 Artiodachjla 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 witli 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, does 
not appear to us to be necessary, and we shall therefore 
adhere in the present work to the old orders, Rumi- 
nantia and Pachydermata. 
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 
