98 FOSSIL JAWS OF MACROPODID.H, 



exteriorly, increasing in depth posteriorly. Lower contour line 

 straight or arched upwards. Incisor proclivous, spatulate. 

 Symphysis lax. 



Dimensions. 



Mandibular. — The full series of cheek-teeth is from 55*8 to 

 58-6 in length (2); the first three molars 30-1 to 31-6 (2); the 

 premolar 12-1 x 6-8 to 12-8 x 7(2). The Mddth of m."^ is from 

 8-9 to 10-5. The anterior depth is from 26-1 to 28-5 (4); the 

 posterior from 29*0 to 32-7 (4); the thickness from 14-8 to 15-6 



Fo7'm.. 



Man(lihulai\ — P.-^ (PI. xvi. fig, 9). This tooth as exemplified 

 by the anterior two-thirds of its crown in a mandiliular fragment 

 is structurally similar to its successor p.^, but the extero-posterior 

 complicated region of the crown is not evidently marked off by an 

 oblique cleft. On the outer surface of this region there is a 

 distinct trace of an outstanding cusp corresponding to that in p. ^ 

 of S. jmles. 



Molars. — Mr. Lydekker's statement that in Sthetuirus there are 

 no " vertical folds " must be understood to refer only to the lateral 

 processes of the longitudinal links, as the latter exist in S. gollnh 

 and S. otuel. Of the presence in the type of the genus of tapering 

 folds lying upon the anterior surface of the lobes as we have seen 

 them in all the species now referred to it there is no doubt; there 

 is indeed evidence of the fact in the figure of m.-^ in II. PL 82, fig. 

 9, though no mention of it is made by Owen. In the mutilated 

 tooth now figured (PL xvi. fig. 11) from a mandil)le having the 

 characteristic premolar rising into place the incumbent folds are 

 well marked fully in the hind lobe and by their bases in the 

 broken fore lobe."^ 



* Complication of structure is more frequently found in the anterior 

 molars than in the posterior; nay, even the fore lobe of the last molar 

 rather than in tlie hind. It is therefore unsafe to pronounce teeth free 

 from folds unless the young jaw is found without them, or to neglect the 

 slightest trace of such folds which may remain in worn teeth. 



