CHANGES FOR ADAPTATION IN THE MOLE SOL, 
vertebrae are almost uniform in shape except that the fourth 
has a median process extending anteroventrally from the cen- 
trum. In some cases a similar projection occurs on the fifth 
lumbar, but when present it is very small. I have not deter- 
mined the function of this process. It is completely covered 
by the psoas magnus muscle and may serve to increase the sur- 
face for its attachment. The sacral vertebrae are so closely 
fused in the adult that they form a continuous bone to which 
the pelvic arch has become ankylosed for almost its entire 
length. 
According to other investigators, the number of ribs varies 
from twelve to fourteen in different species. In the two American 
species under observation there are fourteen pairs. They are 
very slender and pliable, thus permitting great flexibility of the 
animal. This pliability is due not only to their small diameter, 
but also to the attachment to the vertebrae and to the greater 
ratio or proportion of cartilaginous portion to bony portion. 
The attachment at the proximal end is such as to allow relatively 
free movement and the large proportion of cartilage permits 
easy bending. The average ratio of the bony to the cartilaginous 
portion in Scalops is 1.4 to 1. In man it is approximately 5.43 
Ole 
The ribs are so fragile that fracture frequently occurs during 
life. Evidence of such a break is seen on the sixth rib in figure 1. 
All the ribs are ribbon-like and measure from 1.2 to 2 mm. wide 
and 0.4 to 0.5 mm. thick. Their length is quite variable as seen 
in table 2. . 
The first rib is 10.8 mm. long and the seventh or longest 
measures 44.3, an increase of over four times. These results 
are at great variance to the statement of Bell (’39) who says, 
“The ribs in the mole and its congeners are nearly all of the 
same length, giving the peculiar cylindrical form to the body 
which characterises these animals, and which is so essential to 
their habits.’ Plate 1 shows that the thorax has the typical 
cone-shape characteristic of mammals. The transverse diame- 
ter of this cone at the level of the first rib is 7 mm.; at the level 
of the ninth or tenth rib it reaches its greatest dimension of 34 
