TOOTH-DEVKLOPMKNT IN OKNITHOEHYNCHUS. 139 



'Jlie latter^ it is clear^ innst derive its origin from that small, 



papillated enamel-organ which Ponlton described and figured 



in his mammary-foetal stage. The two large anterior teeth 



in Stewart's specimen are, of course, the same as the two 



large and partly calcifi.ed enamel-organs present in Professor 



Poulton's specimen. In the upper jaw Stewart found "a 



small, oval, soft papilliform elevation, which apparently 



corresponded with the most anterior of the three pairs of 



teeth found by Mr. Poulton,'' whilst the second and thii'd 



very large foetal teeth were represented by large mnlticuspi- 



date teeth, like the two anterior teeth in the lower jaw, to 



which teeth they appear to correspond. On the other hand, 



in the upper jaw there appears to be no representative, in tlie 



adolescent animal, of the enamel-organ representing the 



fourth tooth stated by Ponlton to be present "in a very early 



stage " or condition of development, and corresponding to the 



early papillated enamel-organ which he figures from the lower 



jaw. 



Professor Stewart concludes that 'Hhe complete dental 



3 3 



formula would, as far as at present known, be ^ -„, as sur- 



o — o 



mised by Mr. Poultoii." These last words are surely due to 



an oversight, for Professor Ponlton clearly expresses the 



4 — 4 

 surmise that the complete dental formula should read -j ~. 



Nevertheless, the above analysis of Professor Stewart's 

 contribution indicates that it is far from certain that the 

 actual teeth of the upper jaw in the adolescent animal corre- 

 spond, each to each, with the three teeth of the lower jaw^ 

 It is obviously rather improbable either that the large anterior 

 tooth of the lower jaw should be the genuine opponent of the 

 small anterior tooth of the upper jaw, or that the small 

 posterior tooth of the lower jaw should, similarly, correspond 

 to the very large tooth which is the posterior one in the- upper 

 jaw of the adolescent animal. And we have also to take 

 account of Poulton's definite statement that he found behind 

 the second large tooth of the upper jaw a tooth- rudiment in 



