The Nautilus. 



Vol. IV. APRIL, 1891. No. 12. 



MOLLUSKS OF THOMPSON'S LAKE, ILLINOIS. 



iTRODK, .M. D., BERNADOTTE, ILL 



Tlie beautiful Anodonta snborbic'ihifa of Say has a sjiarse dirtri- 

 bution and is rarely f )iind in considerable numbers. 



Ikno\vofl)ut one locality in Illinois where it is to be found in 

 abundance. This j)lace is a still beautiful lake, five miles long by 

 one in breadth, with an average depth of from five to eight feet; the 

 bottom a mixture of black mud and sand ; the shores and a hundred 

 acres or so at each end covered with a growth of pond Lilies. 



For a half century this lake has been a great fishing resort. 

 With seines five hundred yards long, trammel and funnel nets, 

 hook and line, spears, etc., immense quantities of fish are annually 

 taken from its waters ; great Buffalo, Cat-fish, Shovel-fish, Jack- 

 salmon and a half dozen kinds of Sunfish, Bass, Pike and Pickerel. 



State Geologist Worthen (deceased) seems to have been the only 

 naturalist who discovered the conchological richness of the lake, 

 and he kept the discovery to himself, collecting large quantities of 

 the Ano. suborbiculata Say and corpulenta Cpr. and sending them 

 to collectors and museums all over the world. 



In the summer of 18U0 I made a careful search for the Unionidse 

 and found it containing but four species: Unio anodoutoides Lea, 

 and parvus Bar., and Ano. suborbiculata Say, and corpulenta Cpr. 



But the abundance of the two Anodontas make up for the lack 

 of species. In some places the bottom of the lake seemed to be lit- 

 erally paved with the suborbiculata. With a six-tined potato-dig- 



