8 THE NAUTILUS. 



C. Baker's " Mollusca of the Chicago Area," he cites the collec- 

 tion of this species under such conditions. By correspondence 

 with Mr. Baker I learned the names of the collectors^ who 

 kindly gave me directions for locating the species which they 

 had taken many years previous. The first five specimens I 

 found were not gravid ; so that I feared it was too early or too 

 late. Upon examination with a microscope all proved to be 

 males. Returning to the stream again I found 9 gravid mus- 

 sels out of a total of 17. The first of these contained glochidia 

 which corresponded exactly with the glochidia found on Nec- 

 turus in the Mississippi, thus giving me the link I desired to 

 make out the life history. 



The glochidia are clear white in color, of the triangular type 

 with well-developed hooks, contrary to the description given by 

 Lea, who however suggested the possibility of hooks in more 

 mature specimens. The dimensions are as follows : Height 

 0.265 to 0.274 mm., length 0.247 to 0.555 mm. 



All of the adult individuals were found under fiat stones of 

 the flag-stone type characteristic of the limestone in the region. 

 Beneath a single rock I found four. While exploring the 

 under surface of these I felt and seized a wriggling animal which 

 proved to be a mud-puppy, demonstrating the manner in 

 which Necturus becomes inoculated. Glochidia shed by the 

 mussels in such a location would not have a rapid dispersal by 

 currents so that the Necturus commonly seeking such a shelter 

 would run the chance of a heavy infection. The finding of a 

 mussel parasitic upon a salamander as the appropriate host in- 

 stead of a fish is the first instance I have known recorded among 

 American mussels. Faussek ^ in St. Petersburg experimented 

 with Amphibia artificially infected with glochidia of Anodontas. 

 He reported successful infection upon Axolotl and Proteus. 



Anodonta imbecillis : — While endeavoring to identify the gloc- 



1 1 wish here to acknowledge the kindly assistance and courtesies extended 

 to me by the following gentlemen : Mr. F. C. Baker, Chicago Academy of 

 Sciences; Messrs. J. B. Brown, J.H. Ferriss, J. H. Handweik and Dr. Alfred 

 Houston, of Joliet, 111., and Mr. Bryant Walker, of Detroit. 



* Faussek, 1901. Ueber den parasitismus der Anodonta-Larven. Verhand- 

 luDgen des V. Internationalen Zoologishen-Congresses (Berlin), pp. 761-766. 



