CHANGES FOR ADAPTATION IN THE MOLE 359 
posteriorly, and has a looser connection with the sacrum and 
weaker pubic symphysis.’’ This possibility may be offset, as 
shown farther on, by the fact that there is a very firm bony 
connection between the pelvis and the sacrum in moles. 
All the bones of the normal pelvis are present. These bones 
have been so coéssified that the lines of union are practically 
obliterated. An attempt has been made to indicate their 
boundaries as nearly as they could be determined in figures 4, 5, 
and 6. : 
Wiedersheim says that the ‘pars acetabularis’ in the mole 
(Talpa) is strongly developed and ‘‘shuts the ium as well as 
the pubis out of the acetabulum: in by far the greater number 
of mammals the pubis only is thus excluded.” 
Figures 2 to 6 show that the pelvis has been greatly narrowed 
and that the sacral vertebrae have completely coalesced with the 
ilium and ischium; the space between the sacrum and pelvis is 
thus entirely bridged by bone with exception of two pairs of 
foramina (figs. 2 and 5). This bridge is 18 mm. long in an antero- 
posterior direction and constitutes about 64 per cent of the entire 
length of the pelvis. The pelvis of the species of Scalops under 
consideration has the following dimensions: Extreme length, 
from anterior end of ilium to posterior tip of ischium, 27.8 mm. 
Width, at posterior tips of ischia, 9.56 mm.; at anterior ends of 
ilia, 9.8 mm.; from socket to socket, 6 mm. The dorsoventral 
diameter in the region of the acetabulum from the dorsal margin 
of the ischium to the pubic bones is 4.5 mm. From the dorsal 
edge of the spinal crest through the acetabulum to the pubic 
bones is 7 mm. The transverse diameter of the pelvic outlet 
at the posterior margin of the pubic symphysis is 3 mm. (fig. 7) ; 
at the anterior margin it is 2mm. The dorsoventral dimensions 
at these same regions are 1.5 mm. and 1.25 mm., respectively. 
At the anterior margin of the pubic symphysis a sharp median 
wedge-like projection extends ventrally from the centrum of the 
sacrum to within 1 mm. of the pubic symphysis. The pelvic 
outlet in this region is thus almost divided into two very small 
passages, each about 1 mm. in diameter. The change in the 
location of the alimentary and urogenital tracts which result 
from this condition will be discussed later. 
