40 



Description of the Teeth. 



The teeth of the Mylodon are eighteen in number, arranged according to the 

 following formula, |5|= 18: they are simple, long, fangless, and of the same 

 thickness from the implanted to the exposed end ; the former is excavated by a 

 deep conical pulp-cavity*, the latter worn into a shallow depression, with a raised 

 obtuse margin. The forms of the grinding surfaces are so accurately given in 

 Plates IV. and VI., — those of the upper jaw being represented of the natural size, 

 — that verbal description may be dispensed with. The exserted parts or crowns 

 are unusually worn down, and rather obliquely, so as not to reach the level of the 

 inner wall of the socket in the upper jaw, nor that of the outer wall in the lower 

 jawf. 



The first tooth of the upper jaw, which, as the figures express, is separated 

 by a marked interval from the rest, is also more curved, the convexity being 

 turned forwards ; the posterior teeth are nearly straight : their length is about 

 three inches, the first is a few lines longer than the rest. 



In the lower jaw, the first tooth opposes the second upper molar when the 

 jaws are naturally closed ; but the nature of the joint would allow considerable 

 extent of motion forwards and backwards, and the bony attachments for the 

 masseter show its peculiar adaptation for working the jaw extensively in the hori- 

 zontal direction. The grinding surface of the first lower molar is worn down 

 obliquely, the anterior edge being the highest ; its curvature is outwards and for- 

 wards. The last tooth of the lower jaw, which is the largest and most complex 

 of the series, is slightly bent with the convexity turned inwards. 



Each tooth has a central body of vascular dentine J, in which the medullary 

 canals run parallel with each other obliquely to the axis of the tooth, and form 

 loops at the periphery of the central constituent : this is inclosed by a cyUnder 

 of hard unvascular dentine §, about one line and a half in thickness : the outer 

 covering consists of cement |1, about one-third of a Une in thickness. The unvas- 

 cular dentine, as the densest constituent, forms the prominent ridge inclosing the 

 central depression of the grinding surface. 



* This is indicated by the dotted line in the teeth figured in Plate V. figs. 5 and 6. 

 + In Plate II. the teeth are figured a little more protruded than in the skull itself. 

 I Plate XXIV. fig. 3. a. § Ibid. b. \\ Ibid. c. 



