194 ROYAL NORTON CHAPMAN 
3. The pelvic bones of the marsupial mole 
Attention must be called to the marsupial mole (Notoryctes) 
in this connection (fig. 16). Huxley (75) considered the mar- 
supial pelvis to be inclined to form a large angle with the sa- 
crum, as is the case among marsupials in general, but, in the 
case of the marsupial mole, the pelvis is horizontal and is firmly 
coéssified with the sacrum. Furthermore, the symphysis is 
greatly reduced (fig. 17), which is another departure from the 
usual condition among the marsupials and an approach to the 
condition found among other burrowing mammals. 
From the above consideration of the pelvis of burrowing 
mammals it is clear that the pelvis of such a form, regardless of 
the taxonomic group to which it may belong, may be distin- 
guished from the pelvis of mammals in general by -its more 
horizontal position, its more complete ossification with the 
vertebral column, and by the great reduction or the entire absence 
of the symphysis. In the absence of the symphysis, a pubic 
ligament extends between the two innominate bones. 
Among both the rodents and the insectivors there are forms 
which possess the generalized pelvis with the marked inclination 
and the long symphysis, while, on the other hand, there are 
burrowing forms in both groups which possess the typical 
‘burrowing pelvis.’ 
4. A classification of the pelves of burrowing mammals 
The pelves of the burrowing forms may be classified as: the 
typical burrowing (moles, shrews, pocket gophers, and certain 
meadow mice), in which the ventral margins of the pubic bones 
are horizontal and diverging posteriorly, and the symphysis is 
absent or, when present, formed of a transverse rod of bone 
(figs. 4 to 9 and 12 to 15); the semi-burrowing (mice in general 
and certain insectivors), in which the pubic bones are inclined 
caudoventrad and converge posteriorly to form a symphysis at 
their points of contact (figs. 10 and 11). The typical burrowing 
pelvis may be further divided into the narrow type (moles, 
