888 
*OPLAO[OD Ur01] Upas JO MIIA 9pIG — `I ‘DIA 
THE AMERICAN NATURALIST. [Vor. XXXV. 
found the ordinary larvae of Ambly- 
stoma tigrinum ranging in length 
from one to four inches in the irri- 
gation ditches that were common in 
the San Luis valley in the vicinity 
of Garrison. 
The material was preserved in 5% 
formalin. It contains in all twenty- 
six specimens, with the following 
lengths in millimeters, vzz.: 89, 92, 
98, 100, 103, 105, 105, 105, 106, 
100, 110, £12, 113) 113, 185, 10 
118, 120, 121, 160, 190, 215, 220, 
250, 250, 262. 
Most of the specimens only cor- 
roborate the descriptions of previous 
writers as to the external character- 
istics of these interesting forms, and 
are mentioned here chiefly for the 
sake of making a record of the facts 
and the locality. One of them is in 
a an advanced stage of metamorphosis, 
and has nearly reached the terrestrial 
form of Amblystoma tigrinum. This 
specimen is of especial interest, be- 
cause it is in the act of undergoing 
its development in the midst of its 
natural surroundings. Marsh and 
Tegetmeier, as well as others, have 
described the metamorphosis of sire- 
dons under artificial conditions, but 
I do not know of an account of a 
siredon transforming in its natural 
environment. A number of 
measurements of these specimens 
were made, and are given in 4 
table of measurements at the end 
of this article. 
