The maxillule (plate 5, fig. 1) is well de- 

 veloped. The first inner lobe has 9 strong spines 

 along the internal margin, 4 relatively small 

 spines on the posterior surface, and 1 small 

 spine on the anterior surface. The second and 

 third inner lobes are elongate and have 3 and 



4 setae, respectively. The first outer lobe is low 

 and has 9 setae. The basis bears 4 setae at the 

 apex of the internal margin. The exopod has 

 11 setae. The endopod is 2-segmented, and car- 

 ries 4 -f- 3 setae on the first segment and 6 -|- 

 2 setae on the second. 



The maxilla (plate 5, fig. 2) has 5 well-devel- 

 oped lobes. Each of the first to fourth lobes 

 bears 2 spiniform, spinulose setae of equal 

 length, a short spinulose seta, and a few small 

 spinules near the insertions of the setae. One 

 of the 2 spiniform setae on the fourth lobe is 

 much stouter than the other. The fifth lobe car- 

 ries a strong dagger-.shaped spine in addition 

 to 2 slender setae. The endopod has 6 setae — 1 

 on each of the proximal 3 segments and 3 on 

 the terminal segment. 



The maxilliped (plate 5, fig. 3) consists of a 

 long basipod and a short endopod. The coxa 

 has three groups of 3 setae each and is about 

 as long as the basis, which has a row of spin- 

 ules proximally, 3 scattered setae distally, and 

 2 setae at the extreme apex. The endopod has 



5 segments, which have the following numbers 

 of setae, from proximal to distal : 4, 4, 3, 3 + 

 1, and 4. 



The first pair of legs (plate 5, fig. 4) has 3- 

 segmented exopods and 1-segmented endopods. 

 The coxa has no setae, but bears hairs along 

 the proximal portion of the internal margin. 

 The internal margin of the basis is fringed 

 with hairs and has a curved seta at the distal 

 end. The first exopodal segment lacks setae or 

 spines. The second exopodal segment has an in- 

 ternal seta and an external spine. The Internal 

 margin of the spine appears to be slightly den- 

 ticulate. The third exopodal segment has an ex- 

 ternal spine with a slightly denticulate internal 

 margin. In addition, the .segment has 3 internal 

 setae and a long terminal spine, which has a 

 lamella along the external margin and a row of 

 hairs along the internal margin. Halfway along 

 its external margin the endopod has a round 

 tubercle which has a tran.sverse row of .small, 

 acute spinules. In addition, the endopod has 3 



internal setae, 2 terminal setae, and some 

 small spinules at the base of the middle in- 

 ternal seta. 



The coxa of the second leg (plate 5, fig. 5) 

 has a considerably curved internal margin, 

 which has a row of hairs and a short, thick 

 seta. The basis has no hairs or setae. The exo- 

 pod is 3-segmented. Each of the first and sec- 

 ond segments has an external spine and an in- 

 ternal .seta. In anterior aspect a row of small 

 spinules lies along the distal border of the sec- 

 ond segment. The third segment has 3 external 

 spines, 4 internal .setae, and a dagger-shaped 

 terminal spine armed with 17 triangular teeth. 

 The endopod is 2-segmented, with 1 seta on the 

 first and 5 setae on the second segment, and 

 reaches to about the distal border of the second 

 exopodal segment. 



The basipod and exopod of the third leg 

 (plate 5, fig. 6) are similar to those of the sec- 

 ond leg, but the external spines of the exopod 

 are fringed with fine hairs and the terminal 

 spine is armed with 19 acute, triangular teeth. 

 The endopod is 3-segmented, with 1 seta on 

 each of the first and second segments and 5 

 setae on the third, and extends slightly beyond 

 the distal border of the second exopodal seg- 

 ment. A row of very fine spinules lies along the 

 distal border of the second endopodal .segment. 



The fourth leg (plate 5, fig. 7) differs from 

 the third in the following particulars: About 

 4 small, acute spines are at the insertion of the 

 seta on the coxa. The endopod is longer, reach- 

 ing to a line including one-third of the length 

 of the third exopodal .segment. The terminal 

 spine is also absolutely shorter, and armed with 

 18 teeth along the external edge. The fifth pair 

 of legs is absent. 



Remarks 



The armature of the mandibular blade of the 

 present specimens disagrees with the original 

 description of the species by Brodsky (1950) 

 but agrees with his description for Aetideus 

 armatus. 



I recently compared female specimens of A. 

 armatKs and A. pacificiis from the Pacific coast 

 of North America and found that, although the 

 species are alike in anatomical details of the 

 appendages, they are clearly distinguishable 

 from each other by the size and general shape 



544 



U.S. FISH AND WILDLIFE SERVICE 



