Professor lluxUy — On Falceotherium magnum. 15.3 



III. — On the Milk Diontition of I'dL/icoTJinJiWAJ maosum. 



By rrofessor Huxley, LL.D., F.R.S. 



(PLATE VI.) 



IN tho British Museum there is tlio rit^ht ramus of the mancliblo 

 ot' ii yomv^ Pahv.othennm magnum, obtained by M. liravard IVoiii 

 the Eoceuc strata of Vaucluso, which possesses a peculiar interest, 

 inasmuch as tho three principal milk molars are com})letely cut, 

 though their unworn crowns show that they have not long been in 

 place. Tho ramus itself must have been nearly eight inches long 

 when it was complete, while the distance from tho articular surface 

 of the condyle to the lower margin is about 3-25in. The symphysial 

 surface is oval, rugose, and extends back nearly as far as the anterior 

 margin of the crown of the first visible grinder ; the anterior, or mental 

 region of the ramus, is inclined ui)Avards and forwaixls, and is slightly 

 convex, as in all the true Palceotheria. In front of the most anterior 

 milk molar which is in place, there is an oval fossa about 0-2in. long, 

 which appears to lead into the alveolus of the proper first milk 

 molar (dnv) ; and further forward (but not more than 0-2in., so that 

 the diastema of the milk teeth must have been exceedingly short) a 

 series of depressions on the truncated anterior end of the ramus re- 

 present the bottoms of the alveoli of the canine and incisors. 



The ramus of the mandible of an adult Falceotherium magnum, in 

 the same collection, can hardly have been less than 15 inches long. 

 The diastema between the small first grinding tooth and the great 

 canine is about 0-8in. long, and the symphysis extends back to a little 

 behind the anterior edge of pni^. 



The three milk molars which are in place (viz., drrf^ dm^, and dm'^) 

 in the jaw of the young Palceotlierium, occupy a length of 3*6in., 

 which is identically the same space as that taken up by the second, 

 third, and fourth premolars of the adult jaw. 



The length of the crown of dm'^ ; of pm'^. 



is l-07in. „ 1-lOin. 



„ „ dm^ pm^. 



1-23 „ 1-2 



„ „ dm^ pm^. 



1-25 „ 1-25 



The individual teeth, therefore, correspond in length as nearly as 

 possible. 



The height of the crown, measured from the alveolar margin 

 to its highest point, of dm"^ ; of pm''\ 



is 0-6in. „ 0-9ia. 



„ ,, dm^ pm^. 



0-8 „ 1-0 



„ „ dm* pm*. 



0-92 „ 1-05 



Thus the crowns of the grinding teeth of the adult are all not only 

 absolutely higher than those of the young, but, relatively, they are 

 much higher. The vertical striae on the enamel are also more 



