290 PACIFIC SCIENCE, Vol. XV, April 1961 
FIG. 5. A drawing from the ventral aspect to show the duplicated posterior vena cava, its anastomotic 
branches, and the stellate renal plexus on the surface of the multilobular kidney. 
0.5 cm. high. The sphincter is shaped like a 
signet ring. It is supplied by branches of the 
right phrenic nerve. 
KIDNEYS 
The right kidney lies 2 cm. more cranial than 
the left. The right is 18 cm. long, 8 cm. broad, 
and 3.5 cm. thick; the left is 16 cm. long, 7 cm. 
broad, and 3.5 cm. thick. Each kidney is com- 
posed of large numbers of renules, each about 
2.0 cm. in diameter. The papilla of each renule 
projects into a single calyx with a ductule that 
unites with others to drain eventually into the 
pelvis of the ureter as in Phoca (Harrison and 
Tomlinson, 1956). 
Each kidney is surrounded by a stellate venous 
plexus, the communicating vessels of which lie 
in the sulci between the renules on the surface 
of the kidney. The plexus is more marked on the 
ventral aspect of the organ. There are numerous 
anastomoses with lumbar and lateral wall veins, 
with the intravertebrai vein, and with the azygos 
vein. The plexus is drained mainly by a series 
of tortuous tributaries that extend round the 
upper and lower poles and transversely across 
the ventral and dorsal surfaces of the body of 
the kidney. These tributaries unite at the medial 
border of each kidney to form three or four short 
trunks that enter the two main limbs of the 
posterior vena cava or its large anastomotic 
