16 PE0FESS0E OWEN ON THE CHAEACTEES, ETC. 



in the elevation of different groups of the Lissencephala to a higher 

 place in the Mammalian series, and in their respective association, 

 through some single character, with better-brained orders, according 

 to Mammalogical systems which, at different times, have been 

 proposed by zoologists of deserved reputation. Such, e.g., as the 

 association of the long-clawed Bruta with the Ungulata*, and of 

 the shorter-clawed Shrews, Moles and Hedgehogs, as well as the 

 Bats, with the Camivora\ ; of the Sloths with the Quadrumana^; 

 of the Bats with the same high order§ ; and of the Insectivora and 

 Bodentia in immediate sequence after the Linnean ' Primates,' as 

 in the latest published ' System of Mammalogy,' from a distin- 

 guished French author ||. 



* Macleay, Linn. Trans, vol. xvi. (1833) ; Gray, Dr. J. E., Mammalia in the 

 British Museum, 12mo. 1843, p. xii. 



t Cuvier, Regne Animal, 1829, p. 110. 



% De Blainville, Osteographie, 4to. fasc. 1. p. 47 (1839). 



§ Linnaeus, Systema Naturae. 



|| Prof. Gervais, Zoologie et Paleontologie Francaise, 4to. 1852, p. 194. 

 This scheme is avowedly an adoption of that proposed by Professor Milne- 

 Edwards, in the first volume of the 3rd series of the 'Annales des Sciences 

 Naturelles,' 1844, in a paper entitled ' Considerations sur quelques Principes 

 relatifs h la Classification Naturelle des Animaux,' &c. ; in referring to which, 

 M. Gervais states his conviction that Milne-Edwards, " a mis hors de doute les 

 rapports des Rongeurs avec les premiers Mammiferes." — Annales des Sciences 

 Naturelles, ser. hi. vol. i. p. 251. The high and justly-earned reputation of 

 both these naturalists renders it incumbent on me to state the doubts with 

 respect to the actual affinity of the Rodentia to the Quadrumana which 

 remained on my mind after an attentive perusal of the arguments urged by 

 Milne-Edwards. The first of these arguments is based upon an alleged resem- 

 blance of placental structure, expressed by the term " a placenta discoide," 

 apphed as a character to the Bimana, Quadrumana, Cheiroptera, Insectivora 

 and Rodentia, collectively. 



The degree of resemblance in outward form, between the placenta of the Rat 

 or Hare, on the one hand, and the Mycetes and Macacus on the other, seems 

 to me to be more than counterbalanced by the difference of structure. The 

 pedunculate and cotyloid placenta of the Rat consists of foetal parts exclusively ; 

 the maternal areolar portion is as distinct from it as it is in the cotyledon of the 

 Ruminant, and is a persistent structure of the uterus. The discoid placenta of 

 the Monkey includes a large proportion of maternal cellular structure, which 

 comes away with the foetal portion. The difference in the organic interblending 

 of the circulatory organs of mother and offspring, between the Rodentia and 

 Quadrumana, is of much more real importance than the degree of superficial 

 similarity. Still more significant, in regard to genetic grounds of affinity, is the 

 great difference in the development and function of the vitelhcle or umbilical 

 sac in the foetal membranes of the two orders. But, as regards outward form, 

 the cotyloid placenta of the Muridce differs more from the thin, expanded and 

 subdivided placenta of the Hare, than it does from that of the Marmoset Mon- 

 key : then, it signifies something in the argument drawn from similarity 



