A MUSSEL SURVEY OF THE UPPER WATERS OF 

 THE VERMILIOX RIVER WITH SPECIAL REF- 

 ERENCE TO THE SALT FORK^ 



By Frank Collins Baker and Frank Smith^ L^niversity 



OF Illinois. 



Abstract. 



The study was undertaken for the purpose of ascertain- 

 ing the distribution of the mussel fauna of the upper 

 waters of the Vermilion River, Extensive collections were 

 made at definite stations between L^rbana and Homer 

 Park, each station embracing a stretch of the stream 

 measuring 500 feet or more. The water was fairly low 

 during the 191S season and it was possible to give the bed 

 of the stream a most searching study. This was done 

 either with the bare hands or with a Walker dredge for the 

 smaller species. 



Thirty-two species, representing 12 genera, were ob- 

 tained. Twenty statious were established between Urbana 

 and Middle Fork, near Danville, 12 of which were between 

 St. Joseph and Homer Park, the part of the Salt Fork 

 most thoroughly explored. As would be expected, tne 

 mussel fauna is the least developed in the upper part of the 

 Salt Fork above Crystal Lake, Urbana. where but four 

 species were found. Below the dam at Homer Park the 

 greatest faunal development was seen, 26 species being 

 definitely identified. The dam at this station appears to 

 form a barrier to the migration up stream of several spe- 

 cies, only 16 of the Homer Park mussels occurring in the 

 stream between the dam and the neighborhood of Sidney; 

 10 species appear to reach their limit of upstream distri- 

 bution below the dam. It is possible that the fish carrying 

 the glochidia of these species are not able to pass the dam 

 and do not occur above it. Next to the Homer Park sta- 

 tion, the lower part of the Middle Fork, near Danville, 



* Contribution from the Museum of Natural History, University of Illinois, 

 Number 14. 



129 



