121 



Order PACHYDERMA. 



Family Toxodontida. 

 Genus Toxodon. 



560. The skull, without the lower jaw, of the Toxodon platensis, Owen. 



This fine and unique specimen was discovered in a whitish argillaceous 

 earth, on the banks of the Sarandis, about 120 miles to the north-west 

 of Monte Video, South America. 



Though mutilated and literally broken in pieces when transmitted to 

 the Museum, the cranium was susceptible of the degree of restoration in 

 which it is now exhibited, and demonstrates all those characters from 

 which a general physiological idea may be formed of the nature and 

 habits of the animal, and consequently of its zoological affinities. The 

 remarkable nature of these affinities and the rarity of the specimen ap- 

 pear to call for the following detailed description of it. 



The dimensions of the cranium of the Toxodon platensis amply attest 

 that the animal to which it belonged was of a magnitude attained by few 

 terrestrial quadrupeds, and only to be compared, in this respect, with the 

 larger ordinary Pachyderms, or the extinct Megatherium. The length 

 of the skull is two feet four inches ; the extreme breadth one foot four 

 inches. 



The general form of the skull, without the lower jaw, is semi-ovate, 

 depressed, elongate, of considerable breadth including the span of the 

 zygomatic arches ; but becoming rather suddenly contracted anterior to 

 them, the facial part being considerably produced, and gradually con- 

 tracting to near the muzzle, which again slightly expands. 



Among the first peculiarities which strike the observer, is the aspect 

 of the plane of the occipital foramen, and of the occipital or posterior 

 region of the cranium, both of which incline from below upwards and 

 forwards at an angle of 75° with the basal line of the skull. This slope 

 of the back part of the skull is one of the striking characteristics of the 



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