10 



precedence of the colossal and sagacious elephant in the Cu- 

 vicrian scheme 1 . 



The profound admiration and respect which I have always 

 entertained for my chief instructor in Zootomy and Zoology, 

 never blinded me to the necessity of much modification of his 

 arrangement of the Mammalia. The question, more especi- 

 ally, of the truly natural and equivalent primary groups of 

 the class, has been present to my mind whenever I have been 

 engaged in dissecting the rarer forms which have died at the 

 Zoological Gardens in London, or on other occasions. But I 

 propose first to submit to you, as briefly and clearly as I am 

 able, the results of this store of anatomical knowledge as ap- 

 plicable to the true organic characters of the class MAMMALIA. 



Mammals are distinguished outwardly by an entire or 

 partial covering of hair 2 , and by having teats or mammas 

 whence the name of the class. 



All mammals possess mammary glands and suckle their 

 young : the embryo or foetus is developed in a womb. Their 

 leading anatomical character is, the highly vascular and mi- 

 Fig, i. 



nutely cellular structure of the lungs, (fig. 1, ?,) which arc 

 freely suspended in a thoracic cavity separated by a musculo- 

 tendinous partition or ' diaphragm' from the abdomen, (ib. d.) 



1 The modifications consequently proposed by Geoffroy St Hilaire, Illiger, 

 De Blainville, C. L. Bonaparte, J. E. Gray, Waterhouse, Milne Edwards, 

 Lesson, Wagner, Nilsson, Oken, Macleay, Sir E. Home, Gervais, and others, 

 have been cited and commented upon in my Papers communicated to the Lin- 

 naean Society (Proceedings, 1857) and the Geological Society (Proceedings, Nov. 

 1847, pp. 135140). 



2 The foetal Cetacea shew tufts of hair on the muzzle. 



