188 ROYAL NORTON CHAPMAN 
SPECIES : pol raat OPEN TYPE pees 
Geomys bUTSATIUS.< 5. 2.8 nares Steet em oe 23 9 14 
Geomiys Cuz fae ees eg ake ean a 6 2 + 
Geomiys hispidGs:. xyes seen eae cee a oe ee eee 1 0 1 
Geomys: (species not known): .2...5..4.te0eee4e- 5 1 4 
Thomomiys talpowdesmufescens:!... 2-24 .2e- ase. 2: 3 3 0 
Mhomonmiysiboniaeyoouidelecy 5 see ea eee 3 1 2 
‘Thomomys' bogiae miericans.«.1.---e ome eee. 1 0 1 
Thomonitys ‘bottade pasenlis. 2. aes ace a: oo 3 0 3 
Mhomomiyssbottaeyanicae yee ae ee wee 3 1 2 
Mhomomiysicolumblanussseee eee eee eee 1 1 0 
Thomomys fulvus intermedius.................... 1 0 1 
Rhomomiysmmonticolameazamiaeeee ee eee eee 5 0 5 
Thomomiys quadratusiquaduatisa. «2s ase ae 1 0 i 
These data are based upon specimens in the flesh which were 
dissected to determine the condition of the pelvis and the sex 
of the specimens. 
It is obvious that no conclusions as to the percentage of the 
open and closed types of pelvis in the various species can be 
drawn without the examination of a much more extended series 
of material. This table shows, however, that the closed type of 
pelvis predominates in the females. But the point to be em- 
phasized by a study of the table is, that both the open and the 
closed types of pelvis occur among the females of nearly all the 
species. In every species where only one type of pelvis was 
found, so few specimens were examined that the occurrence of 
the other type is not precluded. 
Aside from these variations with regard to the presence or 
absence of the symphysis, the pelves of the pocket gophers 
present certain characteristics which are constant. The pelvis 
of Geomys bursarius has again been used, in comparison with 
figures from Huxley (’75). The first two caudal vertebrae are 
coossified with the sacral vetebrae and with each other forming 
an extension of the sacrum which arches dorsad in such a way 
that the second caudal vertebra is on a level with the dorsal 
margin of the ischium with which it is coéssified. For this 
reaon the line designated as the sacral axis (Sa) has been drawn 
through the articulation of the sacrum with the ilium and the 
