18 PROFESSOR OWEN ON THE CHARACTERS, ETC. 



less of the cerebellum ; and generally more or less over the olfactory 

 lobes. Save in very few exceptional cases of the smaller and 

 inferior forms of Quadrumana (fig. 3), the superficies is folded into 

 more or less numerous gyri or convolutions, — whence the name 

 Gyrencephala*, which I propose for the third subclass of Mam- 

 malia (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 



volutions iii Stenops tardigradus (Trolik, Reck. d'Anatomie comparee sur le 

 genre Stenops, in N. Verhand. der lste Klasse Koninkl. Nederl. Inst. Amster- 

 dam, Oct. 1843) ; there is, to that extent, in the Quadrumanous order, a 

 superficial resemblance to the non-convoluted brains of the Rodentia and In- 

 sectivora ; but it is attended by that more important difference in the form 

 and proportions of the cerebral hemispheres, of which I express my estimate by 

 the system of Classification proposed in the present paper. 



The smooth hemispheres of the brain of the Midas (fig. 3. a) " extend, as in 

 most of the Quadrumana, over the greater part of the cerebellum (c)" (Phd. Trans. 

 1837, p. 93) ; it resembles, in short, the brain of the Human embryo before the 

 cerebral surface begins to be folded ; whereas hi the Insectivora, in the Beaver, 

 and even in the Capybara, in which there are a few shallow aiifractuosities, the 

 cerebral hemispheres leave the cerebellum quite exposed. 



With regard to the alleged contrast between the brains of the Rodentia and 

 Carnivora, in the breadth of the anterior and middle part of the cerebral 

 hemispheres, a comparison of the brains of the Beaver and Coatimoiidi, and of 

 the Porcupine and the Civet Cat, leaves me entirely unable to appreciate the 

 force of the remark. 



The third argument for the high position of the Rodentia, Cheiroptera and 

 Insectivora in the Mammalian scale, is deduced from some particulars of their 

 osteology, and principally from the common presence of the clavicle in them, 

 as contrasted with its constant absence in the Carnivora and Ungulata. The 

 clavicle is present in all Quadrumana, but it is not a peculiar characteristic of 

 the higher forms of the Mammalian class. It is much more constant in the 

 class of Birds and Keptiles : it is present in the Monotremes, in Marsupials, 

 and in most Bruta. An affinity of the Insectivora and of the claviculate 

 Rodentia with a lower vertebrate type, might therefore be inferred from the 

 clavicle, at least with as much reason, as with the Apes and Man. As to the 

 shape of the articular cavity for the mandible, the Rodentia differ more from 

 the Quadrumana in this particular than the Carnivora do ; whilst, in respect 

 of the size, form, and persistent individuality of the tympanic bone, the 

 Rodentia plainly show then" more essential relations to the oviparous type ; 

 the Carnivora resembling the Quadrumana in the early coalescence of the petro- 

 tympanic with the squamosal elements of the temporal bone. 



Such are some of the considerations which have induced me to set a different 

 value than M.Grervais does, on the arguments adduced by Prof. Milne-Edwards 

 in favour of an association of the Rodentia with the Quadrumana, in a highly 

 placed primary group of the Mammalian class. 



* yvpoo), to beml or wind ; eyxe<pa\os, brain. 



