91 



The other specimens accompanying the former, and suspected to belong to 

 the same species, consist of fragments of three lower jaws, containing each 

 one or two molar teeth. One of the specimens contains the first and second 

 molars and the remains of the last one. The portion of jaw is like the corre- 

 sponding portion in Notharctus, but is thicker and the teeth are stouter. The 

 teeth are considerably worn, as represented in the view of the triturating sur- 

 face of the second molar in Fig. 38, Plate VI, magnified two diameters. The 

 crown is oblong square, and consists of two divisions, each of which, in the 

 unworn condition, presented, an acute crescentoid summit In the abraded 

 condition the divisions present two broad, semi-lunar tracts of dentine con- 

 tinuous with each other. The tracts embrace, internally, shallow enameled 

 recesses,. of which the posterior is much the larger. The contiguous horns 

 of the tracts are continuous upon a tubercle at the inner part of the crown 

 just in advance of the middle. The posterior horn of the posterior crescent 

 is likewise continuous, with a tubercle at the postero-internal angle of the 

 crown. Externally the latter is bounded by a basal ridge, and an clement of 

 the same occupies the postero-internal angle of the crown. 



Measurements of the specimen are as follows : 



Lines. 



Depth of jaw below the middle molar • 6h 



Space occupied by the three molars . 9 



Breadth of crown of first molar 2i 



Width of crown of first molar : 2 



Breadth of crown of second molar 3 



Width of crown of second molar 2£ 



A second specimen consists of a nearly corresponding portion of another 

 jaw containing the first and second molars. The jaw-fragment is of greater 

 depth than in the former, but otherwise is about as robust, and the teeth are 

 nearly of the same size. The measurements are as follows : 



Depth of jaw below middle molar b{ 



Linos. 

 4 



Breadth of crown of first molar 2 J 



Width of crown of first molar 2J 



Breadth of crown of second molar 2| 



Width of crown of second molar 2£ 



Two additional specimens consist of portions of both rami "of the lower jaw 

 of a younger animal than the preceding, but only one contains a single tooth, 

 the first molar, which is represented in Fig. 39, Plate VI, magnified two 

 diameters. The rami of the jaw are of more slender proportions than indicated 



