472 MB. M. F. WOODWARD ON MAMMALIAN DENTITION. [May 2, 



v.— EXPLANATION OF PLATES XXXV.-XXXVII. 



In all cases the teeth represented are frum the left side, and when shown in 

 section are looked at from the front, so that the left of the Plate represents the 

 inner side of the jaw. 



Fig. 1. Jaws of Petrogale (113 mm. long), clarified, and showing the tooth- 

 germs in situ, {'■-i'^, the 6 upper incisors ; i^-i^, the 3 lower incisors ; 

 c, canine; p}?i^, pin*, pm^, pm^, the upper and lower premolars 

 «i^, »!j, the 1st upper and lower molar ; pms, the premaxillo-maxil- 

 lary suture. 



2. Wax model of the enamel-organs of the 1st and 2nd upper incisors ; 



lettering as above, d.l, dental lamina ; i'-' , rudiment of successional 

 tooth. 



3. Transverse section of the enamel-organs of the 3rd and 4th upper 



incisors of Petrogale. 



4. A wax model showing the relation of the 4th upper incisor (i*) to the 



5th (P) and 6th {i^). Petrogale. 



5. Transverse section through the oth (i^) and 6th (t^) incisors oi Macropzts 



eugenii. i^\ rudimentary successional tooth. 



6. Transverse section through the upper 4th and Oth incisors (z* and i^) 



with the rudimentarj' successor to the latter {i^'). The vestigial ."jth 

 incisor (e^) is dotted in to show its relative position. M.giganieim. 



7. Transverse section through the developing 1st incisor of M. giganteus. 



i", successional tooth. 



8. Trausverse section through the enamel-organ of the 4th incisor and its 



rudimentary successor, i*'. M. giganteus. 



9. Section taken parallel with the median plane of the head, but transverse 



to the dental lamina, passing through the 1st and 2nd lower incisors 

 (/j and »,). Petrogale (95 cm.). 



10. Enlarged drawing of the 1st lower incisor (?',), showing its advanced 



calcification and its rudimentary successor i/. Petrogale (11 cm.). 



11. Transverse section through the 2nd lower incisor of M. gigantetis. 



7.2, rudimentary successor. 



12. Section through the dental lamina between the canine and 3rd premolar, 



showing a slight differentiation, possibly representing one of the 

 missing premolars. Petrogale. 



13. Ditto. M. eugenii. 



14. Section in front of the 3rd lower premolar, M. giganteus, showing the 



missing 2nd premolar. 



15. Section through the enamel-organ of the 3rd premolar. Petrogale. 



16. Section showing the earliest indication of the so-called 4th successional 



premolar (2)pm). Petrogale (9'5 cm.). 

 166. Section through the same region as 16 a in an older embryo. 11 cm. 



17. Section showing the character of the dental lamina between figs. 15 and 



16 or 16 and 18. Petrogale. 



18. Enamel-organ of the 4th premolar ; 2^ possibly represents the last trace 



of a successional tooth. Petrogale. 



19. A drawing of a was model showing the relation between pm^ and pm* 



and the permanent premolar (pjnn). Petrogale. 



20. Section through the enamel-organ of the 3rd premolar of M. giganteus. 



21. The dental lamina between pni^ and pm*, already .slightly swollen, the 



earliest appearance of the successional tooth {ppm). M. giganteus. 



22. The enamel-organ of the 4th premolar. M. giganteus. 



23. Section through the 3rd premolar and the germ of the so-called 4th 



successional tooth {ppm). M. eugenii. 



24. Ditto, ditto. Mpyprymnus rufescens. Showing the relation of the 



hitherto supposed successor ( ppm) to the 4th premolar to pni^ and 

 pm^. 



25. a,b. The developing germs of — oi Petrogale. — , the milk-rudiments; 



- , , the germs of the functional and permanent teeth. 



