206 ROYAL NORTON CHAPMAN 
for the support of the viscera in the absence of the symphysis. 
In both groups there are cases, certain pocket gophers and the 
South African golden mole, where the symphysis is absent and 
the rectus abdominis muscles are not crossed, but in both groups 
provisions for the support of the viscera are constant. 
SUMMARY 
This paper is based upon a study of structures in animals 
belonging to different systematic groups but which have similar 
habits. All of the forms are found to agree in the general 
structure of the pelvis which is correlated with the habits, and 
the minor differences in the structure are correlated with specitic 
differences in the habits. 
The moles (Talpidae), so well adapted to the burrowing habit, 
possess horizontal pelves which are firmly codssified to the 
vertebral column, the ventral margins of the pubic bones are 
horizontal and diverge from each other posteriorly, and the 
symphysis pubis is absent. In some cases (Scaptochirus and 
Mogura) a second symphysis is formed dorsal to the viscera, 
contributing to the greater strength of the pelvis. 
The pocket gophers (Geomydae), also well adapted to the 
burrowing habit, possess a horizontal pelvis firmly codéssified to 
the vertebral column, and have the ventral margins of the pubic 
bones horizontal and diverging from each other posteriorly. 
The symphysis, however, is present in the males and in some of 
the females, while it is absent in others even of the same species. 
There are other rodents (meadow mice, Microtinae) and in- 
sectivors (shrews, Soricidae) which possess similar pelves with 
various degrees of specialization. These forms live in runways 
in the debris which covers the ground, and the degree of their 
specialization is correlated with the depth to which they drive 
their tunnels. 
The marsupial mole (Notoryctes) has a habit similar to that 
of other moles and has departed from the marsupial type of 
pelvis, as is shown by the firm codssification of the pelvic bones 
with the vertebral column, the greatly reduced symphysis, and 
the horizontal pelvis. 
