NO. 1788. NORTH AMERICAN ERGASILID^— WILSON. 389 



in three large curved claws, graded in size, the outer one a little more 

 than twice the length of the inner. Beneath them the joint sends 

 out a rough and flattened process, which reaches the tip of the second 

 claw. From the anterior proximal corner of the second joint a stout 

 curved claw projects inward toward its fellow on the opposite antenna, 

 and the two nearly meet at the mid-line. 



The mouth-parts are close behind the antennae; they consist of a 

 well-defined upper lip, a pair of mandibles, two pairs of maxillae, 

 and one pair of maxiUipeds (fig. 41). The upper lip is transversely 

 elliptical, twice as long as wide, with a fairly regular outline. The 

 mandibles are three-jointed, the joints diminishing regularly in size; 

 the basal joint starts out perpendicularly from the surface of the head 

 and is then bent over inward at a right angle, carrying the last two 

 joints beneath the upper lip. The terminal joint is conical, twice as 

 long as wide, and covered with fiiie hairs. 



The maxillary hooks are attached to the raised edge of the disk 

 which surrounds the other mouth-parts; each consists of a rounded 

 base and a stout curved claw. The first maxillse are in the form of 

 knobs, each armed with three widely divergent seta?. Each second 

 maxilla has two joints beside the terminal blades, the proximal one 

 much longer and stouter than the distal. The terminal blades are 

 attached side by side, the dorsal or superior one twice the length of 

 the ventral, both entirely covered with short hairs. 



The maxillipeds are immediately behind the maxillae; the basal 

 joint is elongate, triangular in outline, with the apex extending for- 

 ward and inward, and is fused to the surface of the head. From the 

 anterior apex the slender and cylindrical terminal joint is turned 

 backward in an S curve, as in Bomolochus. This terminal joint is 

 only about half the length of the basal and ends in two stout, non- 

 plumose settfi of unequal length. 



The first four pairs of legs are biramose, with three-jointed rami, 

 tlie joints in the exopods of the first pair being thoroughly fused. 

 The arrangement of the spines and setae is as follows: First exopod, 

 0-0; I-O; 1-5: endopod, 0-1; 0-2; 0-7: second exopod, I-O; I-l; 

 III-6: endopod, 0-1; 1-2; II-4: third exopod, I-O; I-l; 1-7: endo- 

 pod, 0-1; 1-2; II-3: fourth exopod, I-O; I-O; II-2: endopod, I-O; 

 II-O; II-6. The fifth legs are uniramose and two-jointed; the basal 

 joint is very narrow and short and is armed with a small spine on its 

 anterior border. The terminal joint is enlarged into a broad ovate 

 lamina, tipped with four short spines. 



Color a dull white throughout, the ovaries and oviducts a deeper 

 shade than the rest of the body. 



Total length, 2.64 mm. Cephalothorax, 0.6 mm. long, 0.88 mm. 

 wide. Length of free segments, 1 mm.; of egg-strings, 1.53 mm.; 

 of anal setae, 0.6 mm. 



