394 
Psyche 
[December 
origin, having been formed as crystallization products in 
connection with fossilized wood that was silicified in ex- 
tinct hot springs. 
As a brief examination of the voluminous literature on 
caddis-worms has yielded no definite statements relative 
to the part played by vision in the choice of case-building 
material, it has seemed appropriate to present the accom- 
panying observations. 
I have not been able to determine the larva accurately, 
but it is structurally very similar to that of Platyphylax 
designatus, and undoubtedly belongs to some rather closely 
related form. Professor Banks has suggested that it may 
quite likely belong to one of two species of Heterophylax 
that are common in that part of the United States, H. 
magnus Banks or H. occidentals Banks. On account of 
their size it is probable that they may be the latter species, 
as this is decidedly the smaller form. 
