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XX. On the ■ Development and Succession of the Teeth in the Marsupialia. By 
William Henry Flower, F.B.S., F.B.C.S., &c., Conservator of the Museum of the 
Royal College of Surgeons of Fmgland. 
Received April 17, — Read May 9, 1867. 
.Although the dentition of adult individuals of the animals which constitute the 
remarkable order, or, rather, subclass Marsupialia, has been repeatedly subjected to 
examination, and described with exhaustive minuteness of detail, it is a singular circum- 
stance that most of those peculiarities of the succession of their teeth which distinguish 
them from other mammals appear hitherto to have escaped observation. 
Professor Owen has, indeed, established the fact that those posterior teeth of each 
side of each jaw which have no deciduous predecessor are, as a general rule, four in 
number, instead of three, as in most placental mammals*, and has further contributed 
some important observations upon the later stages of the dentition of one family, the 
Maeropodidwf . 
Beyond this, I have not been able to find any information upon the subject. Indeed 
it is remarked by the author just mentioned, that “ an interesting field of observation still 
remains open in regard to the period and order of development of the deciduous and 
permanent teeth, in the different carnivorous, omnivorous, insectivorous, and frugivorous 
marsupials.” 
To supply this blank is the object of the present communication. Fortunately the 
materials contained in the Museum of the Royal College of Surgeons, if not quite so 
complete as might be desired, are amply sufficient to illustrate the main aspects of the 
question, and to furnish a result as interesting as it was unexpected. 
Family Macropodidal 
From many observations upon the early dentition of the Kangaroos (genus Macropus ), 
1 will only select for description certain well-marked stages, which are sufficient to 
illustrate the successive steps of the process. 
1. The object of the first observation which needs recording was a marsupial foetus of 
a Macropus of uncertain species, but probably belonging to one of the larger forms. 
Its entire length was 6 ’5 inches, of which the head occupied 1-4 inch, and the tail 
2 inches. The surface was destitute of hair, the margins of the lips were still adherent 
except in front, and the eyelids were completely closed. 
* “ Outlines of a Classification of the Marsupialia,” Trans. Zool. Soc. vol. ii. pp. 315-333 (1839). 
t See especially Cyclop. Anat. and Physiol. Art. “ Teeth,” and Cat. Mus. Roy. Coll. Surgeons, Osteol. Series, 
vol. i. (1853). 
MDCCCLXYII. 4 R 
