Charles F. W. McClure 395 
Type III, C, includes those cases in which the above men- 
tioned dorsal and ventral union are subequally developed. 
Eleven examples of this ype were met with distributed among two 
males and nine females. 
See Figs. 23, 24 (ventral views) and 25 (dorsal view), Plate V. 
Two sets of variations were met with within this Type: 
First, as in Figs. 23 and 24, in which the two internal iliac veins 
anastomose ventral to the A. sacralis media and join the external ilacs 
by means of two vessels, subequal in size, which lie respectively dorsal 
and ventral to the common iliac arteries of opposite sides. In Fig. 23 
the ventral vessel joins the right, while in Fig. 24 it joins the left ex- 
ternal iliac vein. 
Second, as in Fig. 25 (dorsal view), in which the two internal iliac 
veins, without previously anastomosing ventral to the A. sacralis media 
join the external iliac vein of the right side by means of two vessels, sub- 
equal in size, which lie, respectively, dorsal and ventral to the common 
ihac artery of the right side. 
Two PostcavAL VARIATIONS WHICH CANNOT BE CLASSED UNDER THE 
ABOVE THREE TYPES. 
In addition to the variations already described in connection with the 
three Types, two others were met with which differ so widely from them 
in certain fundamental characters that they need a special description. 
The main features which characterize these two cases and distinguish 
them from the variations described under the three Types are twofold: 
(1) All of the posterior tributaries of the postcava unite to 
form this vessel, as in the higher mammals, dorsal to the 
arteries; (2) the postcava lies to the left of the aorta instead 
of upon its ventral surface as in the other cases (Text Figs. VII 
and VIIT). 
The position of the ureters in these two cases was normal in every 
respect. 
The posteava in these two abnormalities resembles in every 
detail that of a higher mammal in which the left instead of the 
right posteardinal vein persists caudal to the kidneys.” 
The two abnormalities differ from each other only in the manner in 
which the internal iliac veins (V.i.i.) unite with the external iliacs 
18The conditions represented by Text Fig. VII are identical to those found in the 
cat when the left instead of the right postcardinal vein persists as the caudal end of 
the postcaya. 
