400 Mr, G. R. Waterhouse on the Classification of Mammalia. 



those numbered 1 to 9 inclusive comprise the nine orders of 

 Placental Mammalia; and the lowest circle, 10, represents the 

 Impkcental Mammals, which in the structm*e of their brain, and 

 in their generative and vascular systems, exliibit the lowest grade 

 of organization observable in the class ; that is, the most remote 

 from man, and the most approximate to the oviparous classes. 



The Placental series appears to divide itself into two great 

 masses or sections, the first or highest of which includes the 

 circles 1 to 4, and the second is represented by the four lower 

 circles, 6 to 9 inclusive. The higher section embraces those 

 species which possess in a well-developed condition the four kinds 

 of teeth, viz. incisors, canines, false molars, and true molars. 

 They are chiefly animals of prey, carnivorous or insectivorous, if 

 we except the highest circle, which contains those mammals which 

 approach in all their characters most nearly to man, and are 

 chiefly frugivorous : here the brain presents at first — that is, in 

 the highest Quadrumana — a structm-e very similar to that of man ; 

 but in the lowest Lemuridoi, which are always placed at the bottom 

 of the Quadrumanous series, we find the cerebrum comparatively 

 small, the anterior lobes in some*, but little developed and con- 

 tracted in front, instead of presenting the rounded and expanded 

 condition as in man. The convolutions of the hemispheres are but 

 few in number and very symmetrical. The cerebellum is in a great 

 measure exposed. In the lowest American Monkeys is a struc- 

 ture of brain which may be regarded as intermediate between 

 that observable in the Lemurs and that of the higher Quadru- 

 mana. Thus in the genus Midas the brain is almost destitute 

 of convolutions, but its superiority over that of the Lemurs is 

 evinced in the comparatively great development of the cerebrum, 



following order: viz. 1. Quadrumana, 2. Cheiroptera, 3. Ferce, 4. Cetaceu, 

 5. Pachydermata, 6. Ruminant/a, 7. Rodentia, 8. Edentata, and 9. Marsu- 

 piata. The MS. catalogue of this collection being prepared early in 1837, 

 was ordered to be published and appeared in 1838. Since the publication of 

 that catalogue I have adopted M. de Blainville's views respecting the In- 

 xecfivora, that is, in regarding them as a separate order. In placing the 

 Marsupial animals at the end of tlie series I followed M. de Blainville and 

 Prof Owen, and was especially induced to do so through the writings of the 

 latter author. 



This classification, which has been adopted by Prof Owen and Mr. Martin, 

 it will be seen, is essentially the same as the one here proposed, though, by 

 placing the orders as in the above table, many important facts may be ex- 

 pressed which could not be displayed by arranging them in a linear series. 

 I ought to observe, that in Prof. Owen's linear disposition of the orders (see 

 the ' Cyclopsedia of Anat. and Phys.' part 21), tlie Edentata precede the Ro- 

 dents, and are not, as in the Catalogue of the Zoological Society's Collection, 

 placed after that group. This change I adopt, but with some hesitation. 



* See Recherches d' Anatomic comparee sur le genre S'teiwps d'llliger, 

 by Prof Vrolik. 



