5 7^ Bulletin American Museum of Natural History. [Vol. XIX, 



posterior sides tend to divide the tooth into two lobes. The 

 posterior lobe is worn obliquely. The greatest length is 

 oblique to the dental series. 



The crown of the third molar is broken off, but the root 

 gives the shape and dimensions of this tooth accurately. The 

 external side is slightly convex, nearly straight. The inter- 

 nal side is slightly concave with indication of a groove in 

 the middle. The anterior and the posterior sides are con- 

 cave, with a faint groove in the middle of each. The greatest 

 length is oblique to the dental series. 



The fourth molar is the largest and most complicated of the 

 series. It is composed of three lobes: a large anterior lobe, 

 oblique to the dental series; a posterior lobe, more than half 

 the size of the anterior lobe, transverse to the series, and a 

 much smaller, less defined middle lobe, connecting the two 

 and parallel to the series. The anterior lobe is convex on the 

 internal and the external sides, concave on the anterior side, 

 with a faint double groove in the middle, and concave on the 

 posterior border, drawn out to form the connecting middle 

 lobe, which unites with it on the internal half of the posterior 

 border. The external and the internal sides of the posterior 

 lobe are convex, and the posterior side is convex, with a 

 slight median groove; the anterior side is convex, uniting 

 with the middle lobe on the outer half. The middle lobe is 

 well defined on the outer face by two deep sulci, and less 

 marked on the internal side by two broad shallower sulci. 

 The anterior and posterior borders are drawn out to form the 

 connecting isthmuses, the latter being twice the width of the 

 former. The posterior and half of the middle lobes of this 

 tooth opposed the last molar of the upper series, and the 

 crown is nearly flat. The anterior lobe opposed the second 

 molar of the upper series, and the crown is worn in a cres- 

 centic surface. 



Ramus, etc. — The ramus of the lower jaw is long and robust 

 but contracts rapidly to the symphysial region. It is thick 

 and massive in the dental portion and expanded in a thin 

 vertical plate posteriorly. The external surface is concave — 

 rounded both vertically and horizontally. The internal sur- 



