544 Wisconsin Academy of Sciences, Arts, and Letters. 
reached where it becomes confluent with the lung tissue on the 
right side of the trachea. 
To the right of the junction of the trachea and the lung an 
anterior projection of the lung receives along its ventral sur¬ 
face the pulmonary artery. Thompson (T4) describes this pro¬ 
jection in TJiamnophis ordionoides as entering the lung through 
a constriction but no such constriction was found in the speci¬ 
mens examined by me. 
The pulmonary vein enters the lung to the left of the pul¬ 
monary artery and is embedded in the tissue of the lining of the 
lung on the ventral side while the artery runs along the exter¬ 
nal, ventral surface of the lung. This is a general condition in 
the snakes with one lung. 
The vascular lining of the lung decreases gradually toward the 
caudal end so that all but the first two or three inches is little 
more than an air reservoir. 
Opposite the pancreas blood vessels were found on the sur¬ 
face of the lung-sack in the specimens of T. sirtalis from Florida. 
In specimen No. 11 they were especially prominent and of large 
size. They seemed to be connected in a reticulation and entered 
the portal vein through at least three trunks, and the vena cava 
through one. I consider this condition to be very unique and 
therefore was very careful to make sure that my observations 
were correct. 
The Visceral Organs. 
The Alimentary Canal. 
The alimentary canal of Thamnophis differs but little from 
that of other serpents. The esophagus and stomach are contin¬ 
uous and are not differentiated. The stomach folds begin in the 
esophagus and become more and more complex and extensive 
as the stomach region is reached. The stomach folds are thrown 
into more complex transverse convolutions than are those of 
Zamenis as judged by preserved specimens. The stomach proper 
is also shorter than in Zamenis (Atwood, ’16). 
The pyloric end of the stomach is reduced to a small tube lined 
with comparatively simple, longitudinal folds. It is very short 
and joins the bluntly rounded stomach proper so that the tran¬ 
sition is distinct. The pyloric valve is simply a constriction of 
