33 



primary divisions or subclasses of the Mammalia; its true 

 equivalency is with the LISSENCEPHALA, and all its analogical 

 relations are to be found more directly in that smooth-brained 

 subclass than in the Placentalia at large. 



The following Table exemplifies the correspondence of the 

 groups in the Lyencephalous and Lissencephalous series : 

 LYENCEPHALA. LISSENCEPHALA. 



Uliizopliaga ] Burrowing Rodentia. 



Poephaga * Dipodidce and Leporidce. 



Petaurus Pteromys. 



Phalangistidce ^ Sciuridce and prehen sile-tailed 







arboreal Eodents. 



PJiascolarctos Bradypm. 



Perameles and Myrmecobius. Erinaceidce. 



Chceropus Macroscelis, 



Diddpliys and Phascogale . Soricidce. 



Dasyuridce Centetes, Gymnura. 



Echidna Manis. 



Besides the more general characters by which the LISSEN- 

 CEPHALA, in common with the LYENCEPHALA, resemble Birds 

 and Beptiles, there are many other remarkable indications of 

 their affinity to the Oviparous Yertebrata in particular orders 

 or genera of the subclass. Such, e. g., are the cloaca, con- 

 voluted trachea, supernumerary cervical vertebrae and their 

 floating ribs, in the three-toed Sloth ; the numerous trunk-ribs 

 in the two-toed Sloth ; the irritability of the muscular fibre, and 

 persistence of contractile power in the Sloths and some other 

 Bruta ; the long, slender, beak-like edentulous jaws and 

 gizzard of the Anteaters ; the imbricated scales of the equally 

 edentulous Pangolins, which have both gizzard and gastric 

 glands like the proventricular ones in birds ; the dermal bony 

 armour of the Armadillos like that of loricated Saurians ; the 

 quills of the Porcupine and Hedgehog ; the brilliant iridescent 

 colours of the fur of the Cape-mole ( ChrysocJilora aurea) ; 

 the proventriculus of the Dormouse and Beaver; the pre- 



1 On the Classification of the Marsupialia, Trans, of the Zool. Soc. Vol. u, 



p. 315, 1839. 



D 



