The Zoologist— July, 1873. 3587 



Mammalia, hypothelically connecting the marsupial and placental 

 divisions by the rodents, through this affinity of the wombat for 

 them. According to natural selection, as I understand it, we should 

 expect to find such a connecting linli, and this evidence at any 

 rate is not antagonistic to the theory. 



But what is to be said about the Thylacinus, the hyena or tiger 

 of the settlers in Van Dieman's Land, a predacious marsupial, the 

 size of a large dog, whose skull is so very similar to that of a dog 

 that a naturalist need be well up in his subject to be able to 

 distinguish it from a dog's if he were to find it lying about on an 

 English common ? 



The dog has sis insignificant incisors above and below ; Thy- 

 lacinus eight above and six below. The dog has two large curved 

 conical canines above and below; Thylacinus precisely similar 

 ones : the lower canines, in both cases, close in front of the upper, 

 although the lower incisors close behind the upper. Next behind 

 the canines in both animals a row of spear-headed teeth are placed 

 to help to hold a struggling prey. The molars of the marsupial, 

 six in each jaw, are formed for cutting flesh and breaking small 

 bones ; two of the teeth in each jaw of the dog are similarly formed ; 

 four posterior ones above and below being tubercular grinders, 

 more adapted for crushing than cutting. The homologies of their 

 respective dental formula are : — 



Thylacinus. 



Incisor. Canine. Premolars. Molars. 



= 2.i 



46 



42 



Any one who will compare the skulls of the badger or seal with 

 that of the dog cannot fail to be struck with the much greater 

 dissimilarity they exhibit than do the two skulls we have been 

 considering ; yet both these animals are indubitably classed with 

 the dog in the same order of Carnivora, far removed from the 

 marsupials. Some naturalists, led no doubt by this fact, classed 

 marsupials as a suborder of Carnivora, but in that case we should 

 only reverse the difficulty by having to account for the homologies 

 of the wombat with the higher rodents. 



