Life of Lower Lake Region. 119 



On Plates XIII and XIV the reader will 

 find a good head with teeth in place and in 

 fine condition. This head measures seven- 

 teen inches in length. The lower molars of 

 the rhinoceros may always be known by the 

 shape of their crowns which take on the like- 

 ness of the letter L, as may be seen on Plate 

 XV. The clumsiness of these bones and 

 teeth has given wider play to the presence of 

 infiltrated quartz, and the agate luster that 

 follows covers the whole surface of the fossil 

 teeth. 



As compared with the fossils of the horse, 

 one is surprised at the small amount of varia- 

 tion of these bones and teeth, a fact that has 

 an explanation in a comparison of their con- 

 trasted environments, the horse being essen- 

 tially an uphill mammal surrounded with wide 

 varying of crag and mountain, the rhinoceros 

 is shut into the dull uniformity of the swamp 

 and lake shore. 



ENTELODON. 



The Suidae, or hog family, is represented 

 in these lower lake beds by several genera 



