406 ON THE FOSSIL BONES OF PACHYDERMATOUS QUADRUPEDS. 



at first a small transverse part, a ; then a pair of knobs, b c, separated 

 by a deep valley from another pair, d e, which are also separated by 

 another valley from a simple knob, f. Mastication has only worn these 

 konbs on their anterior surface, and very obliquely ; a circumstance 

 which shows that the knobs of the opposite tooth penetrated into the 

 intervals of the latter during the process of mastication. 



This constitutes in itself a difference from the ordinary hippopotamus ; 

 but in other respects all the other essential characters meet in this 

 tooth as much as in the last tooth but one of the lower jaw of that 

 great animal ; — the same four knobs in two pairs ; the same isolated 

 knob behind ; the same small transverse prominence in front. If the 

 trefoil figures are not perfectly distinguishable, this is owing to the 

 oblique manner in which detrition takes place : it effaces the longi- 

 tudinal furrows of the knobs, and only leaves some traces of them 

 behind. A little of this trefoil figure is seen in b and in c. 



This tooth is 0,033 in length, and 0,016 in breadth. 



In the block of M, Journu-Aubert I found the germ of this same 

 posterior tooth. It is represented plate 34, fig. 7. 



Another of these teeth, plate 32, fig. 6, is almost square at its 

 base, which is entirely surrounded by a salient collar, upon which 

 arise two pairs of knobs, or rather two transverse knobs forked at their 

 summits, and marked with furrows on their surfaces ; so that, if de- 

 trition had been conducted horizontally, it would most certainly have 

 produced trefoil figures ; but although it is only just begun in this 

 particular tooth, it is already easy to perceive that it takes place ob- 

 liquely. The points of the two knobs in front, a b, are only slightly 

 worn into the shape of a triangle, and yet the part adjoining the collar 

 c is also a little blunted ; which proves that the salient parts of the op- 

 posite tooth penetrated into the cavities of the latter. 



This tooth is 0,027, both in length and breadth, at the circumference 

 of its base. 



A third tooth, similar to the preceding, but smaller and more deeply 

 worn (two proofs of its having been placed more in front), is repre- 

 sented plate 32, fig. 8; its square measures but 0,02 ; itstwo first knobs, 

 a b, have already confounded their osseous discs, owing to the 

 effects of detrition ; the other two, c d, present as yet but two separated 

 triangles. 



Fig. 3, plate 33, is the germ of a tooth, which in time would have 

 become similar to the preceding. It has not emerged from the gum, 

 neither has it got a root, nor is its summit in the slightest degree 

 impaired : we may there see how the two transverse knobs are both 

 rendered forked at their summits by two planes, making together an 

 angle of about sixty degrees. 



The resemblance of this germ to a similar one of the common hippo- 

 potamus, must strike the least attentive observer : it is larger than that 

 of the worn teeth, because it is the way in which detrition is effected 

 which causes all the difference of shape between the two species. 



The base of this germ is 00,23 square : that of the germ of the com- 

 mon hippopotamus, which I have compared to it, is 0,05, that is, more 

 than double. Neither is it so perfectly square, and the posterior knobs 

 are omewhat shorter than the rest. 



