NO. 2063. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 617 



Male . — Unknown . 



Remarlcs. — Gurley in his manuscript identifies the host of Pack- 

 ard's specimens as Salmo mylciss. However that may be, it is very 

 possible that the two lots came from the same host, since the large 

 fish in Colorado are called indifferently trout or salmon. Packard's 

 description and figure leave no doubt of the identity of his species 

 with the specimens collected by Doctor Linton. 



Packard recognized that it was not a true AcJitheres, for he says: 

 "This species should perhaps be regarded as the type of a subgenus 

 of Aclitheres, which it resembles more nearly than Lemaeocera. The 

 abdominal segments are very faintly indicated, and in the form 

 and degree of development of the head and appendages it seems 

 intermediate between AcJitheres and Cauloxenus." 



The additional details here presented show clearly that it belongs 

 to Salmincola. 



Genus ACHTHERES Nordmann. 



Generic cliaracters of female. — Body divided into three regions: a 

 smaU cephalo thorax with the antennal area differentiated dorsally; 

 a plump thorax, more or less distinctly segmented, at least on the 

 ventral surface, narrowed into a well-defined neck anteriorly, where 

 often one of the segments is clearly separated; and a conical abdomen, 

 usually unsegmented, but sometimes (micro pteri) segmented; no 

 posterior processes, anal laminae, or genital process. 



First antennae distinctly three-jointed and tipped with three 

 setae; second antennae biramose, turned down across the frontal 

 margin, the endopod one-jointed, the exopod two-jouited; first 

 maxiUae with two terminal setae and without a palp; maxiUipeds 

 between the bases of the second maxillae, which are separate to the 

 very tip, where they are joined to an ordinary buUa; egg strings short 

 and stout, eggs large. 



Generic cliaracters of male. — Size medium (1 mm.) ; cephalo thorax 

 in line with the body axis, much smaller than the trunk and sep- 

 arated from it by a distinct groove; trunk spindle-shaped, clearly 

 segmented, without an abdomen or anal laminae. First antennae 

 three-jointed; second antennae biramose, the exopod two-jointed 

 and tipped with a claw; first maxillae with two terminal setae and 

 without a palp; second maxillae much longer than the maxiUipeds, 

 the two projecting strongly from the cephalo thorax some distance 

 behind the other mouth parts. 



Type — AcJitheres percarum Nordmann. 



(Achtheres, dxOTjprjc burdensome, annoying). 



Remarlcs.— This genus, as here constituted, includes only species 

 which are parasitic upon fresh-water fishes. Of the eight species six > 

 are North American, and one of them, coregoni, is also found in Swit- 

 zerland. The genus, therefore, may fairly be called an American one, 



