462 
MR. O. THOMAS OH THE TEETH IN THE DASYURIDJS. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Reversed drawing of the right side of the same specimen, to show the 
relative positions of the teeth. 
Lower jaw of Myrmecobius, showing retarded eruption of pm 4 . 
Lower jaw of TriaccCnthodon serrula , showing the germ of the permanent 
pm 4 buried in the bone (after Owen). 
Front of upper jaw of a young Sarcophilus ur sinus, showing retarded 
development of the first incisor. 
The same in Phascologale wallacei. 
Adult Phascologale wallacei , showing relative size of first incisor when 
fully developed. 
PLATE 28. 
Diagrammatic representation of Mammalian tooth-evolution. On the right is the 
main stem of evolution, from the Prototherian to the Eutherian dentition. On the 
left, above, is the Paratherian (Edentate), and below, the continued Metatherian 
branch. 
Main Stem.— I. Generalised Prototherian dentition. 
II. and III. Intermediate stages towards— 
IY. Generalised Metatherian dentition. 
V., VI., and VII. Intermediate stages towards— 
VIII. and IX. Generalised Eutherian dentitions. 
X. to XIII. Examples of specialised Eutherian dentitions : X., 
Elephas; XI., Hydromys; XII., Fells ; XIII., 
Chiromys. 
Paratherian Stem.—Starting from I. or a, the generalised Prototherian dentition. 
/3, Dasypus; e, Bradypodidse, Megatheriidse ; £, Mankhe 
and Myrmecophagidse ; rj, Tcitusia. 
Metatherian Branch.—Starting from L, the Prototherian, to IV., the generalised 
Metatherian dentition. 
IV. a. Didelphys, and most Perameles. 
IV. h. Phascologale, Thylacinus, and some Perameles. 
IV. c. Myrmecobius. 
IV. d. Dasyurus. 
