AIR-BREATHERS 155 
erally circular in outline, brown, thin, and translu- 
cent, and is about a quarter of an inch in diameter. 
Ancylus fragilis, Tryon, the Fragile River-lim- 
pet. Very small, thin, and narrow, limpet-shaped ; 
color, light brown, one-fourth of an inch long. 
From Oregon and California. 
Ancylus subrotundus, Tryon, the Oval River- 
limpet. This little shell is similar to the last, but 
is more oval in outline. It comes from The Dalles, 
on the Columbia River. 
Lanx patelloidea, Lea, the Spotted River-limpet. 
This is a species of fresh water limpet with an 
opaque, varigated shell. It is reported from Shasta 
County, Cal. 
Lanx altus, Tryon, the Tall River-limpet, is also 
reported from northern California. The shell is 
rounded, and elevated in the center. It is probably 
a variety of Ancylus newberryi, Lea, which has a 
very large shell for a River-limpet, sometimes 
reaching the length of 20 millimeters. 
Gundlachia californica, Rowell, the California 
River-limpet, is very minute, limpet-shaped, with a 
small shelf across part of the aperture. It is found 
on the stems of plants growing in stagnant ponds. 
With these little limpet-like shells we take leave, 
for the present, of the ponds and rivers, and turn 
once more to the sea, with all its wonderful wealth 
of animal life, which is inviting us to investigate 
the inhabitants of the great ocean home. 
