NO. 2063. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 629 



Specific cliaracters of male. — Cephalotliorax relatively wider than in 

 ambloylitis, and not separated as distinctly from t'he trunk, the two 

 in the same straight line; trunk spindle-shaped and indistinctly 

 segmented, with a pair of small, claw-shaped anal laminae, curved 

 dorsally; first antenna four-jointed, the second joint nearly as long 

 as the other three, tipped with three short setae; second antenna 

 biramose, the basal portion two-jointed, the joints at an angle with 

 each other, the endopod (dorsal) one-jointed, short, thickset, and 

 terminated by a single spine, the exopod (ventral) two-jointed, the 

 terminal joint inclined dorsally and armed with a large curved claw 

 at the upper distal corner, and three small spines along the distal 

 margin; first maxillae slender and tipped with two stout setae jointed 

 near their bases, palp a mere knob on the inner margin tipped with a 

 minute papilla; second maxillae much longer than the maxillipeds, 

 rather slender but with strong muscles and ending in stout claws; 

 maxillipeds mth a swollen basal joint carrying on its inner margin 

 a corrugated process against which the short terminal claw shuts. 



Total length 2.15 mm. Greatest diameter 0.52 mm. 



Color, a uniform grayish-white. 



(pimelodi, Kr0yer's generic name for the host.) 



Remarlcs. — It is evident from Kr0yer's description that his speci- 

 mens were young females and not fully grown adults. This may be 

 seen in the distinct segmentation, the remnants of the anal laminae 

 and swimming feet, which he mentions as being found on the abdomen 

 and the fii"st thorax segment, respectively. The adults here pre- 

 sented agree so completely in all their general details as to leave no 

 doubt of their identity. The points in which they differ are just 

 those that would be looked for in the two stages of development — • 

 a disappearance of the swimming feet, body segmentation, and anal 

 laminae, and a fusion of the abdomen with the trunk. Hence the 

 presence of these diiferences confirms rather than disparages the 

 identity of the two. 



Probably also the "AcMJieres sp." mentioned by Wright in the 

 Report of the Ontario Game and Fish Commission for 1892 (p. 438, 

 fig. 10, text), is the same as the present species. 



It is evidently not a very common species since the examination 

 of hundreds of catfish by the present author yielded only the three 

 specimens mentioned above. 



ACHTHERES PERCARUM Nordinann. 



Plate 39, figs. 96 and 97. 



Achtheres percaruvi Noedmann, 1832, p. G3, pi. 4, figs. 1-11; pi. 5, figs. 1-12.— Clatts, 

 18G2, p. 287, pis. 23 and 24. 



Host and record of specimens. — The United States National Museum 

 collection contains two lots of this species, the first containing nine 



