456 
Cowbird. Young; in yellow warbler’s nest 
Song Sparrow. 
Indigo Bunting; nesting. 
Northern Yellow-throat. 
Yellow Warbler; nesting. 
Red-eyed Vireo. 
Catbird; nesting. 
Brown Thrasher; nesting. 
Wood Thrush; nesting. 
American Robin; nesting. 
STATION VI. 
Clay hole about twenty feet in diameter in woods on west edge of 
Skokie Marsh, north of Glencoe road. The pool is almost circular 
in outline, but a ditch-like depression has been formed on the 
southwest edge, which extends irregularly for some forty or fifty 
feet. There is no vegetation in or about the pool. Physa inhabited 
the pool by thousands, all, however, being immature. During a 
visit in July they were observed to form a dark border about three 
inches in width entirely around the pool. In the ditch-like outlet 
fully adult Physas were found, as well as Planorbis. 
Only two species were found, the Physa being by far the most 
abundant. These were 
Physa gyrina, 
Planorbis trivolvts. 
During the summer dnd fall, the ditch-like outlet is dry. In 
the clay pit no Planorbes were found, and only immature Physa. 
In the ditch-like depression were the dead shells of Planorbis and 
of adult Physa. Old shells of the latter were marked with four 
well-defined varices, indicating rest periods. 
STATION VII. 
(Plates X., XI. and XII.,1.) 
A marshy pond about three hundred feet in greatest diameter, 
west of the Northwestern Railroad cut-off. The pond is roundly 
ovate in shape. In the spring the water is from one to three or 
four feet in depth, but in late summer and fall the pond is reduced 
to a number of isolated pools here and there and a small wet area 
in the center. 
