Tertiary. | PALZONTOLOGY OF VICTORIA. (Mammalia. 
also showing the 2nd, 3rd, and 4th deciduous molars in place, and the Ist and 2nd true molars ; a 
portion of the 3rd, or last molar, can be seen imbedded in the substance of the bone, not having 
risen into place or use, while the 2nd and 3rd deciduous molars are in place. A portion of the 
bone has been cut out to find the premolar p’, which in such young individuals is imbedded in 
the bone until after the two teeth above it, the deciduous molars d* and d*, have been shed. 
The deciduous molars are marked d*, d*, d‘; the true molars are marked m', m*, m’. (By 
error d? is engraved as 6”). Fig. la, same specimen viewed from above, showing the five 
molars in place in young individuals, d*, d’, d‘, m', m®, with the last molar m* not yet come 
into use, but obliquely set to the line of the others and imbedded in the bone, which exhibits 
it from a fracture in the specimen. This figure shows the complete pattern of the enamel ridges 
of the above-named molars when slightly worn on ridges of the deciduous molars, the two molars 
being unworn by use at the earlier age, also the strong bony union of the two rami of the lower 
jaw in front ; natural size. Fig. 10, same specimen, viewed from inner side, showing the upward 
inclination of the incisors in Procoptodon, characteristically differing from the horizontal or 
procumbent position of these teeth in Macropus. Fig. le, young premolar p* not yet risen to 
replace the deciduous molars d*, d°, viewed from outer side, natural size. Fig. ld, second true 
molar, magnified to show the precise details of the complex ridging of the crown, so distinctive 
from Macropus. Fig. le, pattern of enamel ridging of last molar m* before coming into place, 
natural size. Fig. 1f, form of section of incisor tooth at base of crown. 
Plate LI.—Fig. 1, outer view of portion of jaw of old individual, with the permanent 
molars p, d‘, m', m?, m® in place, natural size (crowns of p* and d! broken). Fig. 10, same 
series of teeth of same specimen, viewed from inner side, natural size. Fig. la, same specimen, 
natural size, viewed from above, showing the three true molars in place, with the pattern of the 
ridging, all worn by use. The crowns of the premolar and deciduous molar p* and d‘ broken 
off. 
NV.B.—The small figures and letters in these plates mark the same teeth as in the text. 
Freperick McCoy. 
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