NO. 1788. NORTH AMERICAN ERG AHI LID M— WILSON . 361 



and ii sliort claw-liko palp at the base of the latter. Second maxillae 

 with a powerful basal joint and a long cutting blade which extends 

 forward diagonally at an angle of about 120° with the basal joint. 



Maxillipeds like those of Bomolochus, except that they are usually 

 without sctte. First swimming legs with very wide rami, armed with 

 large flattened setae; cndopod of the second and often of the third legs 

 similarly widened and armed with flattened setae; exopods of second 

 third, and fourth legs with but three joints like the endopods. 



Male like the female, but with the maxillipeds in normal position 

 behind the other mouth-parts and armed with the usual terminal claw. 



Type-species. — Artacolax (Bomolochus) ardeolse (Kroyer). 



(Artacolax, apxaoj, to hang on and noXa^, a parasite). 



This genus is distinguished from Bomoloclius by the great compara- 

 tive width of the first four thorax segments, by the fusion and over- 

 lapping of the third and fourth segments, so that there are apparently 

 but three free segments in front of the genital segment instead of four, 

 by the abrupt narrowing of the fifth segment, by the increased width 

 of the rami of the first and second swimming legs, and by peculiarities 

 in the structure of each of the mouth-parts, especially the second 

 maxillae. 



ARTIFICIAL KEY TO TIIK SPECIES. 



a. Basal portion of first antenna armed with a large fhitin plate, split anteriorly into 

 throe Kpines h. 



a. JJasal portion of first antenna armed only with setae and tactile hairs, no chitin 

 plate c. 



h. First antennae reaching far beyond the lateral margins; fifth legs made up of two 

 very unequal joints; maxillipeds without plumose setse. .cornutus (Glaus), 18G4. 

 6. First antennse reaching just beyond the lateral margins; fifth legs made up of 

 two very unequal joints; maxillipeds armed with large plumose setse. 



sxtiger, new species, p. .361. 

 b. First antennae scarcely reaching the lateral margin; fifth legs made up of three 

 short joints of equal length; maxillipeds without plumose setae. 



scomber esocis (Kroyer), 1863. 



c. Exopod of first legs three-jointed; fused third and fourth joints as wide as the 



second joint; each anal lamina with three setae of equal length and one 



much shorter chatoessi (Kroyer), 1863. 



c. Exopod of first legs one-jointed; fused third and fourth joints much narrower 



than the second joint; each anal lamina with but two setae d. 



d. Cephalothorax widest at the center and narrowed posteriorly; first abdo- 

 men joint much longer than the others unicirrus (Brian), 1902. 



d. Cephalothorax widest at the posterior margin; the three abdomen joints 

 about the same length ardcolx (Kroyer), 1803, p. 363. 



ARTACOLAX S^TIGER, new species. 

 Plate 51. 



Female. — Cephalothorax semielliptical in shape, but not evenly 

 rounded anteriorly; squarely truncated posteriorly, one-third wider 

 than long. Remaining thorax segments diminishing in width with 



