143] FAUNA OF BIG VERMILION RIVER—BAKER 45 
time, near Lincoln Avenue, and in Crystal Lake. Two summers collecting 
failed to find it common at the present time at these places. Living speci- 
mens were not found in the Salt Fork betwen Spoon River and the big 
bend below the natural dam, a distance of over four miles, and it did not 
occur even infrequently above Homer Park dam, a distance of 17 miles. 
All of the specimens collected are fresh, bright colored shells, greenish 
or olive with distinct grass-green rays. All but one specimen were normal in 
form and coloration. An individual from the cement bridge station was 
thicker than usual, had a short truncated posterior end and somewhat 
resembled small specimens of Sivophitus edentulus. The beak sculpture was 
characteristic of Anodontoides. Pearly growths and abnormalities are 
rare in the shells collected. Gravid females were found September 26 and 
October 8. It seems to be rare in the Sangamon River, only a stray valve 
being found in this river near White Heath. 
17a. Anodontoides ferussacianus buchanensis (Lea). 
Specimens from the Salt Fork near Muncie and from the Big Vermilion 
are referable to this variety, long known under the name subcylindracea 
of Lea. The variety in the Big Vermilion drainage is more elongate, more 
cylindrical, and has a less height in comparison with the length than in the 
typical form. It is also decidedly biangulate behind, a characteristic lack- 
ing in the typical form. At the two localities it is associated with ferussacia- 
nus, but at Muncie it is the prevailing form. 
18. Arcidens confragosus (Say). Rock-Shell. 
This species is a rare inhabitant of the Sangamon River and is not found 
in the Big Vermilion River. It was reported from the Sangamon River at 
White Heath and Monticello by Mr. James Zetek, about ten years ago. 
Professor Smith has not found it at Mahomet during many years of col- 
lecting. Recently (September 1920) a single specimen, dead, was picked 
up by the writer in the Sangamon River at a point about four miles above 
Mahomet, thus establishing its presence above White Heath. It probably 
lives sparingly in the river and may inhabit water too deep for examination. 
It has been reported from the Sangamon at Springfield (Baker, 1906:74). 
19. Lasmigona (Platynaias) compressa (Lea). 
This characteristic species is rare in the Big Vermilion River. Several 
fine specimens were collected from the station three and a half miles above 
Homer Park in riffles on a sand-gravel bottom. One of these shells is 
pathologic, the umbones being almost in the center of the shell, the anterior 
end having a strong depression in front of the umbones. The posterior 
end is much shorter than usual and is rounded instead of broadly truncate. 
The interior shows distomid parasitism near the posterior end with a large 
elongated blister near the postero-ventral margin. The pseudocardinal in 
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