30 



E. M. MUSEUM MEMOIRS. 



zontal line were it not that the median incisor is almost double the size of the 

 canine. The space between the dental series is deeply concave. 



Measurements of the Lower Jaw. 



M. 



Extreme length from infra-condylar depression to symphysis (21 inches) 295 



Depth at last molar 08 



Internal depth of jaw at posterior edge of symphysis 071 



Thickness of jaw at angle 014 



Length of symphysis 15 



The Molar series (see Plate III., Figs i and 2), display three transverse 

 crests, the anterior the most prominent and forming with the second an open 

 angle with the apex directed inward ; the posterior crest, less prominent than 

 the other two and appearing like a much-enlarged cingulum, is serrate through- 

 out the series. A cingulum faint elsewhere is quite strongly developed at the 

 edges of the third crest. Just beyond the inner apex of the middle crests is a 

 large accessory tubercle which is constant on the true molars and last premolar 

 inclusive. 



More in detail, beginning with the last molar — for it presents the characters 

 of all the others in strongest development — it is much the largest of the series. 

 The posterior crest is highest in the centre. The middle crest divides two val- 

 leys, the anterior valley opening outwards, though not completely closed on the 

 inner side. The anterior crest is horizontal, terminating interiorly in a prominent 

 and exteriorly in a lesser tubercle. The second molar presents the same charac- 

 ters, but is greatly reduced in size. The first molar is so much more worn that 

 it fixes three beyond a doubt as the number of true molars. 



In the Premolar series the anterior crest is relatively more prominent, and 

 its terminal tubercles become equal in size. The third is the only premolar 

 on which the tubercle beyond the apex is found. The second and third 

 premolars have the middle crest comparatively lower, while in the first it 

 rises to form a continuous course with the anterior, giving a crescentic appear- 

 ance to this portion of the tooth, accompanied by a considerable elevation of the 

 outer marginal tubercle. 



The Canine-incisor series in Loxolophodon (see Plate III. Figs, i, 3, and 4) are 

 separated by a considerable diastema of about four inches. They are contigu- 

 ous, and directed upward and forward at such an angle that the two lobes, the 

 larger (which is anterior) and smaller (posterior) lobe, are on a line and divide 

 the attrition. They increase regularly in size from the canine forwards. 



The median incisor consists of an outer convex and inner flat surface. The 

 outer portion is divided by a median valley into two convex lobes. Of these the 

 anterior is higher and larger and comes to a pointed apex. The median valley 



