1893.] MB. M. r. WOODWARD 05f MAMMALIAN DENTITION. 461 



the premaxillo-maxillary suture (incisor fissure). The condition of 

 the premolars is very interesting. In the younger of the two 

 specimens examined, the rudiment of the successional tooth is 

 developed very much as in Petrogale, that is in the interspace 

 between pwi^ and jjm*, but it is much closer to the former, with 

 which it is connected, and has no connection whatever at this stage 

 with the latter ; the difference may be, however, due to the fact 

 that this is a slightly older stage than that described for Fetrogale. 

 In the second stage this rudiment of the successional premolar is 

 much more differentiated, and owing to the development of pm', 

 which is here very large, it comes to be under the posterior end 

 and on the inner side of this tooth, with which we have seen it is 

 undoubtedly connected. 



One thing we may say for certain, that in M. hrachyuvus the 

 solitary successional tooth is not developed in connection with jjm*, 

 but either represents a tooth in between pm'*^ and x>m^ or else is 

 the successor to the penultimate premolar {pw?). 



The relation of the premolars in the lower jaw is the same as 

 that in the upper. 



Macropus eugenii. 



Two specimens, 125 mm. long. 



In this species there are present in the upper jaw 5 pairs of in- 

 cisors, corresponding with ?'', i^, z', ?'', and i^ of Fetrogale peincUlata ; 

 and, as in that form, i', i*, and i^ are the functional adult teeth, 

 while i^ and i° are vestigial structures. No trace of that very 

 rudimentary tooth ?^ could be found. Of the rudimentary teeth i' 

 is very small, this being in all probability due to the fact that the 

 first functional incisor here early attains a large size, and has 

 consequently further dwarfed the disappearing r. On the other 

 hand, i^ is a very prominent and well-developed tooth (fig. 5), and 

 in conformity with this we find that t" is at present very slightly 

 developed and quite uncalcified. 



A transverse section across the jaw and passing through i^ and 

 t" is shown in fig. 5, and it will be seen there is a well-developed 

 downgrowth from the inner side of the enamel-organ of i^, 

 showing that this latter tooth, like i' and i*, belongs to the 1st 

 dentition, the do\Migrowth (i'") representing the rudimentary per- 

 manent tooth. The small tooth i' is therefore quite an inde- 

 pendent tooth, and probably represents the 5th incisor of the first 

 dentition. 



Of the first lower incisor (?'J no trace was observed in this 

 species ; the second and functional incisor was large and calcified, 

 and exhibited a large and definite rudiment of its successional 

 tooth in the form of a thick cord-like downgrowth from the inner 

 side of its enamel-organ, this rudiment being more definite here 

 than in any other form I have examined. 



The upper canine is a small tooth situated in the maxilla and 

 close to the last incisor ; it shows no indication of a successional 

 tooth, nor in any form which I have examined can one say 



