94 ON CLASSIFICATION. 



tres mihi occurrere viclentur placentae typi, quorum primus 

 gliribus, secundus feris, tertios simiis et homini proprius est," 



In this passage Mammals are clearly divided, in the first 

 place, into placental and im placental ; and the former are then 

 subdivided into those which have a non-caducous and those 

 which have a caducous uterine placenta. The Cetacea and 

 Ungulate Mammals constitute the former group ; the Rodents, 

 Carnivores, Apes, and Men the latter. 



In 1813, an accomplished English zoologist, Mr. Water- 

 house, published a highly instructive paper on the " Classifi- 

 cation of the Mammalia,"* in which the following passage 

 occurs : — 



"Taking the general form of the Brain into consideration, 

 the placental Mammalia would appear divisible into two 

 sections : first, those in which the cerebrum is generally of a 

 rounded form, obtuse in front and provided with distinct con- 

 volutions ; and secondly, those in which the cerebrum is desti- 

 tute of convolutions, or nearly so, and usually contracted 

 in front. The first division would contain the Quadrumana, 

 Camivora, Cetacea, Pacliydermata, and Piuminantia, and the 

 second would contain the Cheiroptera, Insectivora, Edentata, 

 and Podentia" 



But although Mr. "Waterhouse puts forward thus clearly 

 the facts upon which a cerebral classification of the Mammalia 

 might be based, he immediately afterwards, with his customary 

 judgment, expresses great doubt as to the value of any such 

 classification. 



" But are we in a condition to take for a basis of classifica- 

 tion of the Mammalia the structure of the brain ? I think 

 not, though, in the case of the Marsupialia, it has afforded 

 characters serving to separate that from other sections, and to 

 indicate its proper position in the system. I am not prepared 

 to follow those naturalists who would, in the present state of 

 information, take this organ as one of primary importance in 

 the distribution of the orders of the placental series of Mammals. 

 I cannot adopt the two great sections of this series as apparently 



* "Annals and Magazine of Natural Historv," 1843, vol. xii. ]>. 399. 



