627 



diately posterior to the first, the two appearing in the same section 

 when cut parallel to the symphysis of the premaxillae. 



I should therefore conclude that this vestigial tooth of the Squirrel 

 (Freund 1. c. figs. 7 — 14) was the 2nd incisor in the normal 

 position, while that of the Rabbit was displaced forwards and inwards 

 towards the median line. 



The posterior tooth rudiment of the Squirrel is without a doubt 

 a third incisor and not a canine as Freund has suggested its situation 

 like that of the anterior is by the side of Stenson's canal and there- 

 fore entirely within the limits of the premaxilla, whereas a canine 

 would be placed either within the maxilla or just between that bone 

 and the premaxilla. Judging by the advanced state of ossification of 

 the jaw as seen in Freund's figures (1. c. figs. 8, 9, 10) he should 

 have had no difficulty in deciding the relation of this tooth to these 

 two bones, a point which he does not seem to have paid attention to. 



As I have already pointed out Noack has claimed to have dis- 

 covered a canine in the genus Lepus; now Pouchet and Chabrt, 

 Freund and myself havel investigated the development of the teeth in 

 the Rabbit with especially reference to this point and with the exception 

 of the fact that the first two authors failed to notice the continuity 

 of the dental lamina between the incisors and the premolars 15 ), we 

 are all agreed in the entire absence of any trace of a canine. Per- 

 sonally I have examined most carefully a number of heads of foetal 

 Rabbits of various sizes, by means of complete series of sections of 

 the jaws and in particular the stage described by Noack (head length 

 21 mm), and although I have in some stages been able to trace the 

 dental lamina without interruption from the incisors to the premolarsi 

 but I have utterly failed to find the slightest trace of a canine or of 

 an additional tooth of any description. Yet Noack's canine extends 

 from the premaxillo-maxillary suture to the infra-orbital foramen in 

 the latter bone and would therefore be quite a large tooth. Unfor- 

 tunately no figure is given of this structure and the details are so 

 meagre, that I cannot help thinking that Noack must have been mis- 

 taken especially as he seems to have only worked by means of dis- 

 sections and not by sections, the only method by which we can 

 obtain reliable evidence of these tooth relationships. 



15) I have since found in two specimen each with a head length 

 of 21 mm, that this feature is a variable one as it was completely want- 

 ing in one specimen while in the other the continuity was perfect. This 

 may account for the discrepanoy between Fbeund's observations and those 

 of Pouchet and Chabrt. 



