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 Strophitus 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 rifiles 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 



