MARSUPIALIA. 121 



the circulatory system, the structure of the brain, 

 of the skull, of the palate, and the number of the 

 teeth. 



With the exception of the single genus first known, 

 the Opossum (Didelphys), containing between twenty 

 and thirty species, which are found in North and 

 South America, the whole group is confined to Aus- 

 tralia and the islands adjacent. They afford a sin- 

 gular instance of the isolation of a particular form, 

 and a strong confirmation of the theory, that the 

 centres of creation were not one, but many. They 

 comprise animals of varying size, from the Red Kan- 

 garoo (M. Laniger) which attains the height of man, 

 to the least Flying Squirrel (Petaurus Pygmceus] 

 which is less than the mouse. It is said that no mar- 

 supial animal possesses a true voice ; some of them 

 when irritated, emit a sort of wheezing guttural 

 sound : that of Dasyurus Ursinus approaches the 

 nearest to a growl ; that of the Wombat, is a hiss like 

 that of a serpent: another point of resemblance to 

 the Reptilia. 



DidelphySj* the Opossum. 



The Opossums seem to approach nearer to the 

 structure of ordinary mammals, than any other of 

 the marsupial genera. They possess a well-developed 

 opposible thumb to the hind feet, and the tail is 

 prehensile. The pouch is in some species only ru- 

 dimentary, though in others large and perfectly form- 



* Ava, duo, two, and ^Xip^j, delphys, a womb. 

 VOL. I. G 



