628 PROCEEDINGS OF THE NATIONAL MUSEUM. 



ACHTHERES PIMELODI Kr0yer. 

 Plate 38, figs. 92 to 95. 

 Achtheres pimelodi KR0,yER, 1863, p. 272, pi. 17, fig. 5a and 56. 



Host and record of specimens. — A few youiig females with egg 

 strino-s were obtained by Kr0yer from the mouth of the channel 

 catfish, Ictalurus punctatus (called by Kr0yer Pimelodus maculatus), 

 taken at Cincinnati, Oliio, in 1854. Two adul't females were obtained 

 by the author from the gill arches of the catfish, Ameiurus nehulosis, 

 at Put-in-Bay, Ohio, July 7, 1908. They have received the number 

 39560, U.S.N. M. A single male wa-s obtained from the inside of the 

 operculum of the Fulton cat, Ictalurus anguilla, at Fairport, Iowa, 

 in July 1914; this has been numbered 47726, U.S.N.M. 



Specific characters of female. — General form plump and swollen; 

 cephalothorax almost spherical, a Httle longer than wide and trun- 

 cated anteriorly, its lateral margins shghtly concave, not in Mne with 

 the trunk but incUned at an obtuse angle. Trunk pyrif orm or spindle- 

 shaped in the young females, and flattened dorso-ventrally, with two 

 longitudinal furrows on the dorsal surface; distinctly segmented, the 

 fifth segment much shorter than the others. Abdomen small, 

 conical, inchned ventrally and made up of two segments, the term- 

 inal one much smaller than the basal. 



In the mature adult the segmentation largely disappears, together 

 with the longitudinal furrows, and the abdomen is more or less 

 absorbed into the genital segment. No visible anal laminae, but 

 Kr0yer mentions a pair of very small, blunt, two-segmented (?) 

 lobes at the posterior corners of the abdomen, which are apparent 

 only under pressure. Egg strings as long as the entire animal and 

 linear; eggs large, arranged in two or three rows, from 16 to 20 eggs 

 in a row. 



First antennae directed obhquely outward and forward, slender, 

 pointed, and indistinctly segmented; second antennae large and 

 plump and turned down a'cross the frontal margin; basal portion 

 made up of two equal segments; exopod (ventral) two-jointed and 

 armed at the tip with a small spine; first maxillae very small and 

 plump, each tipped with two setae; second maxillae slender, cyUn- 

 drical, and nearly uniform in size for their entire length ; bulla small, 

 cup-shaped, and practically sessile; maxilUpeds with a medium basal 

 joint having a knob or swelhng on the inner margin; terminal claw 

 much shorter than the basal joint, with a sort of comb made up of 

 three accessory spines on its inner margin. 

 Color, a uniform grayish-wliite. 



Total length (excluding egg strings), 2.8 mm. Length of cephalo- 

 thorax, 1 mm.; of trunk, 1.8 mm.; of egg strings, 3 mm. in the young, 

 2 mm. in adults. Width of cephalothorax, 0.90 mm.; of trunk, 

 1.4 mm. 



