54 Classification of the Mammalia. 



name Gyrencephala, which. I propose for the third subclass of 

 Mammalia (fig - . 4.) 



In this subclass we shall look in vain for those marks of affinity 

 to the Ovipara, which have been instanced in the preceding sub- 

 classes. The testes are, indeed concealed, and through an obvious 

 adaptive principle, in the Cetacea ; but, in the rest of the subclass, 

 with the exception of the Elephants, they pass out of the abdomen, 

 and the Gyrencephalous quadrupeds, as a general rule, have a 

 scrotum. The vulva is externally distinct from the anus. "With 

 the exception, again, of the Elephants, the blood from the head 

 and anterior limbs is returned tc the right auricle by a single 

 precaval trunk. The mammalian modification of the Vertebrate 

 type attains its highest physical perfection in the Gyrencephala, 

 as manifested by the bulk of some, by the destructive mastery of 

 others, by the address and agility of a third order. And, through 

 the superior psychological faculties — an adaptive intelligence pre. 

 dominating over blind irstinct — which are associated with the 

 higher development of the brain, the Gyrencephala afford those 

 species which have ever formed the most cherished companions 

 and servitors, and the most valuable sources of wealth and power, 

 to Mankind. 



In Man the brain presents an ascensive step in development, 

 higher and more strongly marked than that by which the preced- 

 ing subclass was distinguised from the one below it. Not only do 

 the cerebral hemispheres (figs. 5 & 6, a) overlap the olfactory 

 lobes and cerebellum, but they extend in advance of the one, and 

 further back than the other (fig. 6, c). Their posterior develop- 

 ment is so marked, that anatomists have assigned to that part 

 the character of a third lobe ; it is peculiar to the genus Homoi 

 and equally peculiar is the ' posterior horn of the. lateral ventri- 

 cle,' and the ' hippocampus minor,' which characterize the hind 

 lobe of each hemisphere. The superficial grey matter of the cere- 

 brum, through the number and depth of the convolutions, 

 attains its maximum of extent in Man. 



Peculiar mental powers are associated with this highest form o* 

 brain, and their consequences wonderfully illustrate the value of 

 the cerebral character ; according to my estimate of which, I am 

 led to regard the genus Homo, as not merely a representative of a 

 distinct order, but of a distinct subclass of the Mammalia, for 

 which I propose the name of ' Archence.phala? (fig- 6). 



Prosessor Owen then proceeds to subdivide his primary groups 

 into orders. We can only give extracts bearing upon groups of 

 special interest. 



