242 MAMMALS. 



both large, and Professor Owen presumed that the great incisors were used like the canines 

 of the Hippopotamus, to divide or tear up the roots of aquatic plants. The osseous parts per- . 

 taining to the senses of sight and hearing resembled those of the aquatic Rodentia and Pachydermata. 

 The aspect of the nostrils is placed upwards, as in the Sirenia, but they differ in having narrow 

 canals of intercommunication between the nasal passages and the frontal sinus. The articulating 

 condyles of the cranium were thought by Owen to indicate that when the body of the Toxodon 

 was submerged (for Owen appears soon to have come to the conclusion that it must have been a 

 " submerged " animal) the head could be raised so as to form an angle with the neck, and bring 

 the snout to the surface of the water, without the necessity of any corresponding inflexion of the 

 spine. Wlien Owen wrote his description there was no evidence to determine the character of 

 the extremities, whether they were ungulate, unguiculate, or pinnate, while the structure of the 

 nostrils suggested that the habits of the animal were not so strictly aquatic as to warrant the sup- 

 position that the under extremities were altogether wanting. D'Orbigny's discovery of the fore- 

 arm of another species of this genus (T. Paranensis), has proved that it is not a pinnate animal, 

 but has limbs not imlike the Tapir or Capybara. It is to the latter that it seems to me to 

 have most afiinity ; it moreover inhabited the continent which is par excellence the country 

 of Rodents ; and I have accordingly preferred to place it here among the Rodents, instead 

 of to follow Professor Owen, and j)lace it among the Pachydermata. The Capybara, however, 

 roaches a size of no more than three or four feet, whereas, judging by the proportions of the 

 head, the Toxodon must have been at least twelve or sixteen feet in length. 



