Dr. C. W. Andrews — A New Species of Tetrahelodon. 349 



posterior end of m. 2 is indicated by a flat, roughened surface of 

 triangular form, the anterior angle being continuous with the alveolar 

 edges of the symphysial groove. There are three nutritive foramina on 

 the outer surface of the javr. They are separated by nearly equal 

 intervals of about 5 "5 cm., and the hindermost is about opposite the 

 hinder end of the symphysis. 



Of the teeth, the incisors have been entirely lost and the last molars^ 

 alone remain, the second having been already shed before the death 

 of the animal. The last molars are in a not very advanced state of 

 wear, the posterior lobes being as yet untouched. Each (Fig. C) 

 consists of four transverse ridges and a posterior lobe. Each ridge is 

 composed of an outer and an inner portion distinctly separated. The 

 outer tubercles give a trefoil pattern in wear, while the inner are- 

 imperfectly divided into an inner and an outer portion. There is 

 a tendency to the alternation of the outer and inner portions of the 

 ridges, the inner tubercle being situated opposite the anterior lobe of 

 the outer trefoil, the posterior lobe of which almost blocks the- 

 transverse valley. There are also some small accessory tubercles in 

 the valleys. The posterior lobe of the tooth consists of an inner and 

 an outer tubercle and a cusp, imperfectly divided into two, forming 

 the extreme posterior angle of the crown. The cingulum is developed 

 on. the outer side of the tooth, opposite the openings of the transverse 

 valleys. The whole crown is very low, but at the same time it seems 

 to have been thickly covered with cement, which nearly fills the 

 valleys. The specimen described above appears to indicate the existence 

 of a species widely different from those previously described from 

 this horizon. The only forms with which it might be compared are 

 Tetrahelodon euhjphodon, T. campester, and T. proavus of Cope. From 

 the former of these it is distinguished by the much greater deflection 

 of its symphysial region and the larger number of ridges in its 

 last lower molar. T. campester has a much more slender and less 

 deflected symphysial region. In T. proavus also, judging from Cope's 

 figure, although the symphysis is more mas.sive than in T. campester, 

 it is much less bent down than in the present species, and the whole 

 jaw seems to be more slender. 



The dimensions of this specimen are — 



cm. 

 Length from condyle to tip of symphysis ..... (approx.) r26*5 

 Length from posterior end of m. 3 to tip of symphy,sis . .... 93'5 

 Length of symphysis . . . . . . . . . .63"6 



Width of ascending process (approx.) 27'0 



Width between condyle and tip of coronoid process ..... 22-5 



Depth of symphysis at hinder end . . . . . . . .21*0 



Vertical diameter of socket of tusk ...... (approx.) ll-O 



Transverse diameter of socket of tusk ..... (approx.) 7*5 



Depth of mandibular ramus at symphysis . . . . . . . 21'& 



Depth of mandibular ramus opposite anterior edge of ascending process . . 16*0 

 Thickness of mandibular ramus beneath m. 3 . . . . . . 16-0 



Depth of concavity of upper surface of the hinder end of the symphysis . 5 •() 



Width of concavity of upper surface of the hinder end of the symphysis . 7*5 



Width between the posterior ends of the molars .... (approx.) 18-0- 



Length of last lower molar 24:'0 



Width of last lower molar 8"7 



