1 16 SKETCH OF THE HISTOEY Or MAMMALIA. 



points we may refer to the ' Proceeds. Geol. Soc. Lond.' 

 1837; and the 'Zoology of the Beagle: Fossil Mam- 

 malia.' We may observe, however, that "in the aspect 

 of the plane of the occipital foramen and occipital region 

 of the skull, in the form and position of the occipital 

 condyles, in the aspect of the plane of the bony aperture 

 of the nostrils, and in the thickness and texture of the 

 osseous parietes of the skull," the toxodon manifests an 

 affinity to the dinotherium and the aquatic Pachyderms 

 (the herbivorous Cetacea of Cuvier, but which in man- 

 ners and organization have little relationship to the true 

 whales, excepting as far as they are all modified for the 

 waters of the deep). 



Fig. 79. 



With respect to the limbs of the toxodon, we have 

 as yet no evidence respecting their form or number ; 

 how far, therefore, they were constructed for aquatic 

 progression, whether for this solely, or for occasional 

 visits to the land, is yet a problem to be solved. Pro- 

 fessor Owen, however, suggests that the presence of 

 large frontal sinuses renders it not improbable that the 

 habits of this species were not so strictly aquatic as the 

 total absence of hinder extremities would necessitate. 



In speaking of the dinotherium and toxodon it will 

 be seen that we have referred them, with the lamantins 

 and dugongs (more properly duyongs), to the a(|uatic 

 Pachyderms, between which group and the ordinary 

 Pachyderms we regard the hippopotamus as forming a 



