VERTEBRATA. 239 



the most remarkable is that which Professor Owen laid before 

 the Linnean Society in 1857, based on four leading modifications 

 of the brain. In the " first and lowest primary group or sub- 

 class" Lyencephala the cerebral hemispheres are smooth and 

 without folds, leaving the olfactory ganglions, cerebellum, and 

 optic lobes more or less exposed [Monotremata, Marsupialia]. 

 (2) Lissencephala : cerebral hemispheres with few folds ; olfac- 

 tory lobes and cerebellum exposed, but a corpus callosum present 

 [Bodentia, Chiroptera, Insectivora, Bruta]. (3) Gyrencephala : 

 hemispheres folded into more or less numerous " gyri," and 

 extending more or less over the cerebellum and olfactory lobes 

 [Cetacea, Ungulata, Quadrumana]. (4) Archencephala : hemi- 

 spheres more folded, overlapping the olfactory lobes and cere- 

 bellum [Man only]. The last character was said to be peculiar 

 to the genus Homo, and also " equally peculiar" were the ' poste- 

 rior horn of the lateral ventricle ' and the ' hippocampus minor,' 

 " which characterize the hind lobe of each hemisphere." But 

 these characters are now known to exist in the ourang-outang 

 and all the higher Quadrumana. 



Milne Edwards and Alphonse Milne-Edwards have given a 

 classification of the Mammalia as below : 



Primiere sous-classe Mammiferes normaux. 

 Phalange des Hematogenetes. 

 Legion des Micrallantoides. 



Cohorte des Primates (Bimanes, Quadrumanes). 

 Cohorte des Plebeiates (Chiropteres, Insectivores, Ron- 



geurs). 

 Legion des Mesallantoides (Carnivores, Pinnes ou Am- 



phibies). 



Phalange des Hyraciens. 

 Phalange des Proboscidiens. 



Phalange des Megallantoidiens (Pachydermes solidongul6s, 

 Pachydermes bisulques, Camelides, Tragulides, Pecorides). 

 Phalange des Edentes. 

 Deuxieme sous-classe Pinniferiens ou Mammiferes Piscif rrues 



(Sirenides, Cetaces). 

 Troisieme sous-classe (Marsipiaux, Monotremes). 



The Mammalia are divisible into Non-placentals and Placentals. 

 In the former De Blainville includes two subclasses Ornitho- 

 delphia (=Monotremata) and Didelphia (~ Marsupialia), while 

 the latter corresponds to his third subclass Monodelphia. 



