233 



The anterior three divisions of the crown are nearly alike in size and con- 

 struction. The fourth division is less well developed, and consists of a pair 

 of conical lobes, but" the inner is much smaller than the other, and is connate, 

 with a supplemental lobe in advance. Back of these there is a small conical 

 tubercle, corresponding with the heel or rudimental fifth division of the crown 

 in M. americanus. 



In the plaster-cast of the Maryland tooth, the fourth division of the crown 

 consists of a pair of nearly equal conical lobes, embracing a smaller pair 

 at their fore part. Behind these there is a pair of conical tubercles corre- 

 sponding with the single one in the California tooth. The differences indi- 

 cated between the posterior extremity of the crown of the latter and the 

 cast of the Maryland tooth are not greater than those observed between the 

 same teeth of different individuals of M. americanus, and are therefore unim- 

 portant as distinctive characters. 



Well-developed elements of a basal ridge, in the California tooth, occupy 

 the outer fore part of the crown and the intervals of the outer lobes. Between 

 the posterior three divisions of the crown they are better marked than in the 

 cast of the Maryland tooth, or even than is usually the condition in the 

 American mastodon. The ridge is also distinctly produced around the outer 

 part of the third and fourth external lobes and the back of the crown, which 

 is not the case in the cast, nor usually in M. americanus. 



The jaw-fragment containing the tooth is too much mutilated to ascertain 

 anything of importance in regard to it, other than that it measured about (U 

 inches in depth at the fore part. 



Comparative measurements of the California tooth, the cast of the Mary- 

 land tooth, and two teeth of M. americanus arc as follows : 





California. 



Maryland. 



M. americanus. 





Female, j Male.* 



Fore and aft diameter of crown 



Linen. » 

 75 

 33 

 25 

 25 

 1G 

 24 



Lines. 



75 

 -33 



28 



20 



20 



22 



Lines. 

 75 



38-42 

 33 

 28 

 20 

 22 



Lines. 

 90 



Breadth, at anterior three ridges 



41-45 



Breadth at fourth ridge 



Height of third inner lobe, unworn 



39 

 34 



Height of fourth inner lobe 



30 



Height of fourth outer lobe 



30 



heel 



The specimen of the tooth of a male has live transverse divisions to the crown in addition to a small 



30 g 



