62 



formula, Triconodon tlifl'i-rs in tlic close and unbroken array of the several teeth in the same 

 ramus. The mandible is shorter in proportion to its depth; it maintains this depth more 

 equably from the ascending ramus to the symphysis : the anterior contour bends up 

 abruptly from the lower one, instead of the gradual rise and continuation forward to the 

 end of the symphysis, as in all the known Stonesfield Mammals, 1 and as in the existing 

 MyrmecobiuB (PI. I, fig. 24). 2 



The chief value of the specimen (PI. Ill, fig. 10, nat. size) lies in the repetition of the 

 characters of the symphysis! angle, and the almost straight course, or feeble undulation, 

 of the lower border of the mandibular ramus, as in that of the type-jaw (fig. 7) of Trico- 

 nodon mordax. 



Triconodon (?). Plate III, figs. 15, 16, 20. 



The subject of fig. 15, PI. Ill, is part of a right mandibular ramus of a 

 young Mammal allied to and perhaps of the genus last described. The main cone of a 

 premolar {p) is rising into place. The tooth marked m ], but which might be the last 

 of the premolar series, has a low main cone, boldly convex externally, with a low anterior 

 basal cusp, and a large posteriorly produced hind cusp, making the fore-and-aft length of 

 the crown exceed its height. The foremost compressed cone of the succeeding molar and 

 part of the succeeding cone of the same tooth are preserved. Near the fractured fore 

 end of the ramus two or three outlets of the dental canal are discernible. 



The inferiority of size, as compared with fig. 9 or with the type of Triconodon mordax 

 (fig. 7), seems to be more than individual immaturity would account for, and I hesitate 

 either to affirm or deny its specific identity. 



The more mutilated ramus (PI. Ill, fig. 16), of the same size as the preceding, and 

 with a like straight contour of the lower border of the jaw, is figured and here noted 

 with the view chiefly of calling attention to similar better preserved specimens, in 

 the event of such being obtained, capable of throwing light upon the true nature of the 

 subjects of figs. 15 and 16. 



Fig. 20 is chiefly an impression of a similar sized ramus, with a well-preserved canine and 

 impressions, w r hich at the hind part of the molar series recall a Triconodont character. 



Triconodon (?). Plate IV, figs. 5, 5 a. 



The subject of PI. IV, fig. 5, a and b, nat. size, and 5 a, magn. 3 diam., is a 

 portion of a right maxillary bone, with the antepenultimate and penultimate molars, and 



1 lb., figs. 15, 17, 19. 



2 lb., fig. 18. 



