70 
FOSSIL JAWS OF MACMOPODIDjE, 
yield reliable estimates of dimensional extremes and averages 
within the species, and accurate views of the extent of likeness 
and difference in form and size maintained among themselves by 
the species. Information of this kind has been obtained from 
-179 skulls, namely, of Macropus giganteas 80, M. rufus 9, M. 
robustus 39, Halmaturns parryi 55, //. agilis 29, H. dorsalis 88, 
H. ruficollis 50, H. coxeni 9, 11. thetidis 19, H. wilcoxi 2, H. 
siigmaticus '3, H. ualabatus 8, //. browni 1, Ouychogcde frenata 4 
Prtrogale penicillata 70, Dendrolagus lumholtzi 3. Furnished 
with this instruction and with a resolution to be chary of assuming 
anything of a fossil which may not be predicated of a similar 
living species, it may be possible to thread the maze before us 
with more confidence in the progress made than would be per- 
missible were the clues less frequent. 
Since the mutilations to which the fossil remains have been 
subjected diminish in number the available points of comparison 
between them and recent jaws, those data only have been asked 
from the latter which are given with more or less constancy by 
the former. 
As to measurements, the following are those which have been 
found the most useful in practice. The length of the full series 
of cheek-teeth and its width as represented by that of m 3 , the 
molar most frequently preserved in the fossil state : the length of 
the premolars, permanent and deciduous: the external length of 
the mandible from the edge of the masseteric fossa to that of 
incisive outlet: its internal length from the edge of the intermas- 
seteric foramen to the symphysis: its vertical height, anteriorly 
at the fore end of the tooth m 1 , and posteriorly immediately 
behind m 4 : and the thickness of the bone below m 3 . Of less 
frequent service are the length from the hinder end of the sym- 
physis to the incisive outlet, the length of the diastema, that of 
the basiocranial axis, the breadth of the palate, and the height of 
the alveolar process behind the orbit. 
The following tables, which may be of some use to others 
engaged in similar work, are summaries of the measurements 
taken under the headings which seemed most important. An 
