1950] 
Humes and J amnbach — Parasitic Water-mite 
87 
Summary 
Najadicola ingens is reported from 43 localities in Massachusetts, 
Rhode Island, Vermont, New Hampshire, Maine, Quebec, and New 
Brunswick, after an examination of 3077 fresh-water clams from 
74 localities in New England and adjacent areas of Canada. The 
mite parasitizes principally two host clams, Anodonta cataracta and 
Elliptio complanatus, and occasionally Lampsilis radiata. 
The smaller and presumably younger A. cataracta and E. com- 
planatus are parasitized more often than larger individuals. In A. 
cataracta the mites occur mostly in the outer suprabranchial cham- 
bers, but in E. complanatus in the inner suprabranchial chambers. 
The walls of the suprabranchial chambers containing mites almost 
invariably bear numerous papillae. The presence of mites in gravid 
gills apparently interferes with the normal use of the gill as a 
marsupium. 
Literature Cited 
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