622 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 47. 



First antennae slender and distinctly three-jointed; endopod of 

 second pair with tiny and simple spines in place of the large toothed 

 ones of the female; exopod indistinctly jointed, with a minute terminal 

 claw; mandibles and first maxillae like those of the female; second 

 maxillae not as long as in ambloplitis, less than twice as long as the 

 maxillipeds, each tipped with a chela composed of two claws of 

 about the same size, the tip of the anterior one shutting into a 

 hollow in the posterior one; maxillipeds with very stout basal joints, 

 furnished with powerful adductor and flexor muscles; on the inner 

 side of the basal joint is a raised papilla armed as in the female. 



Color, an almost snow white. 



Total length, 1.5 mm. Greatest diameter of trunk, 0.34 mm. 



(jnia'optei'i, the generic name of the host). 



Remarks. — This species is fairly common on both the small- and 

 large-mouthed black bass. The female may be distmguished from 

 ambloplitis by the large abdomen, with its basal lobes and distinct 

 segmentation, and by the much smaller egg strings. This distinction 

 may then be confirmed by the presence of large toothed spmes on 

 the second antennae m micropteri, and their absence in ambloplitis 

 and by the first maxillae which are three parted in micropteri, but 

 only bipartite in ambloplitis. The male may be distinguished by its 

 much larger size and by the chelae on the tips of the second maxillae. 



ACHTHERES LACAE Kr0yer. 

 Plate 35, figs. 70 to 74. 

 Achtheres lacae Kr0yer, 1863, p. 274, pi. 17, fig. 6. 



Host and record of specimens. — Kr0yer found in the Vienna Museum 

 two females with egg strings, which had been labelled Achtheres 

 lacae by Kollar, and were said to have been taken from the mouth 

 of a North American perch, called by Kr0yer " Perca laca.'' 



Eight females with egg strings were obtained from the gills of the 

 striped bass, Roccus lineatus, October 8, 1886, in the Potomac River. 

 They are numbered 12031, U.S.N.M. One has been chosen as a 

 surrogate type of the species and has received the number 43567, 

 U.S.N.M. 



Specific characters o/" /emaZe.— Cephalothorax ovoid, shorter than 

 the trunk but considerably longer than wide; dorsal antennal area 

 narrow, concave along the lateral margins and not continuous 

 posteriorly. Trunk spindle-shaped or ovoid, segmentation very 

 obscure, surface smooth and evenly rounded; abdomen in line with 

 the thorax, small, conical, and distinctly segmented, and wholly in 

 front of, or ventral to, the egg strings. It is one-third as wide and 

 one-quarter as long as the trunk and shows up prominently from 

 every point of view. Egg strings ellipsoidal, shorter than the trunk 

 and about the same diameter as the abdomen; eggs fairly large. 



