462 MR. M. F. WOODWARD OV MAMMALIAN DEXTITTOK. [May 2, 



definitely to which dentition this tooth is to be referred. Between 

 the canine and the premolar the dental lamina branches out in a 

 most curious way, in some sections exhibiting three or four down- 

 growthp from its adamantine face (fig. 13). Whether these repre- 

 sent modifications of the missing premolars 1 and 2 I am unable to 

 say, hut it is interesting to note that a somewhat similar condition 

 of the dental lamina was observed in Petror/ale in the same region. 



The anterior premolar (3rd) is present in the form of a long 

 tooth-germ, which does not as yet show the formation of any 

 dentine or enamel. A careful examination of a complete series 

 of transverse sections revealed on the inner side of this tooth a 

 long cord of epithelium A^hosc nock was anteriorly and superficially 

 connected with the dental lamina at the point of origin of the 

 3rd premolar (fig. 23, ^)y»»), while posteriorly its deeper-seated 

 extremity or bulb was swollen and situated rather behind and 

 deeper in the gum than this tooth. This structure entirely dis- 

 appears from the sections before the 4th premolar is reached, thus 

 showing that it is situated anteriorly to the latter, with, which it at 

 no time shows any connection. 



The same condition holds for the lower jaA^- save that the 

 bulbous portion of this epitheloid cord (xTm) grows backward 

 from its point of origin into the space between the two premolars 

 and eventually attains a situation by the side of the 4th premolar, 

 but it never has any connection with the latter, and its posterior 

 position as compared with the same structure in the upper jaw 

 is probably due to the backward extension of the great lower 

 incisor, which takes up all the room under the 3rd premolar, so that 

 this developing premolar is backwardly displaced until it attains a 

 position imder the 4th premolar. 



The 4th premolar is a very large and well-developed tooth, the 

 largest in either jaw at the stage, and possessing well-developed 

 calcified cusps. It shows no signs of a veHical successor at either 

 of the two stages which I have examined in this species. 



The molars were in both specimens too advanced to show the 

 vestiges of the other dentition, so I was unable to determine to 

 which set they should be refered. 



Macropus giganteus. 



Material consisted of 8 pouch-specimens, a very complete series, 

 youngest about 15.5 mm, long (this specimen was a little older than 

 the largest Petrogale examined). 



In the youngest specimen there were three rudimentary incisors 

 present corresponding to those in Petror/aU, but in all the older ones 

 f had disappeared and both rand i% which were very large to begin 

 with, had now become through absorption very much reduced. 

 These three teeth haxe preciselv the same relation and origin as in 

 Petrof/ale, and so call for no further description. All three func- 

 tional incisors, viz. i\ t"*, i", show at one stage rudiments of their 

 representatives in the second dentition (figs. 6, 7, 8). The first 



