35 



y we seem at first to descend in the scale by finding in 

 that wave-brained subclass a group of animals, having the 

 form of Fishes : but a high grade of mammalian organization 

 is masked beneath this form. 



The GYRENCEPHALA are primarily subdivided, according to 

 modifications of the locomotive organs, into three series, for 

 which the Linnean terms may well be retained ; viz. Mutilata, 

 Ungulata and Unguiculata, the maimed, the hoofed, and the 

 clawed series. 



These limb-characters can only be rightly applied to the 

 gyrencephalous subclass ; they do not indicate natural groups, 

 save in that section of the Mammalia. To associate the 

 LYENCEPHALA and LISSENCEPHALA with the unguiculate GYREN- 

 CEPHALA into one great primary group, as in the Mammalian 

 systems of Ray, Linnasus and Cuvier, is a misapplication of a 

 solitary character akin to that which would have founded a 

 primary division on the discoid placenta or the diphyodont 

 dentition. No one has proposed to associate" the unguiculate 

 Bird or Lizard with the unguiculate Ape; and it is but a 

 little less violation of natural affinities to associate the Mono- 

 tremes with the Quadrumanes in the same primary (unguicu- 

 late) division of the Mammalian class. 



The three primary divisions of the GYRENCEPHALA are of 

 higher value than the ordinal divisions of the LISSENCEPHALA ; 

 just as those orders are of higher value than the representative 

 families of the LYENCEPHALA. 



The Mutilata, or the maimed Mammals with folded brains, 

 are so called because their hind limbs seem, as it were, to have 

 been amputated ; they possess only the pectoral pair of limbs, 

 and these in the form of fins : the hind end of the trunk 

 expands into a broad, horizontally flattened, caudal fin. They 

 have large brains with many and deep convolutions, are 

 naked, and have neither neck, scrotum, nor external ears. 



The first order, called CETACEA, in this division are either 

 edentulous or monophyodont, and the latter have teeth of one 

 kind and usually of simple form. They are c testiconda,' and 



D2 



