42 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.18 



Uropod 1 extending backward to end of uropod 2; rami equal in 

 length, subequal to peduncle ; upper margins of both rami spinulate. 



Uropod 2: rami subequal in length, subequal to peduncle; inner 

 margin of inner ramus and outer margin of outer ramus spinulate, apex 

 of outer ramus with a long spine. 



Uropod 3 : rami subequal in length ; broadly lanceolate, outer ramus 

 narrower than inner; apical outer margin of inner ramus and inner 

 margin of outer ramus strongly setose. 



Telson: lobes tapering evenly to apex; apex strongly notched, with 

 2 setae ; dorsal surface of each lobe with 2 setae. 



Pleon segment 3 : posterior edge convex, lower posterior corner 

 strongly produced into a tooth. 



Pleon segment 4: slightly raised posteriorly, ending acutely above 

 segment 5. 



Pleon segment 6 with low lateral ridges. 



Length of female, 9 mm. 



Description of male: Antenna 1 reaching to end of peduncle of an- 

 tenna 2 ; antenna 2 as long as body, peduncles typically setose ; pleon seg- 

 ment 4 with a deep notch, followed by a large, hood-like process, the 

 posterior edge vertical. 



Material examined: Stations 887-38 (1), 1160-40 (1), 1168-40 

 (2), 1169-40 (2), 1194-40 (2), 1202-40 (1), 1229-41 (13), 1245- 

 41 (1), 1319-41 (1), 1379-41 (6), 1384-41 (8), 1386-41 (4), 1388-41 

 (6), 1390-41 (4), 1418-41 (11), 1471-42 (8). Burch Station 3837 (1). 



Remarks: There has been considerable discussion in the literature 

 regarding this species' relationship to Ampelisca eschrichtii Kr^yer and 

 the problem of bipolarity. All the specimens at hand correspond to 

 the diagnosis of A. macrocephala by Stappers (1911); the most im- 

 portant characters in separating these two species appear to be (1) the 

 lack of a small tooth at the lower posterior angle of coxae 1 and 2, 

 although the corner is slit in the present material; (2) the smooth an- 

 terior margin of article 5 of peraeopod 5; (3) the long spine on the 

 outer ramus of uropod 2 ; (4) the nearly straight lower edge of the 

 posterior lobe of article 2 of peraeopod 5. All of these are characteristic 

 of Ampelisca macrocephala. Stappers also mentions that the outer ramus 

 of uropod 2 is somewhat shorter than the inner ; this is true in the pres- 

 ent material only in the older specimens. Stephensen (1925) questions 

 Holmes' determination of A. macrocephala at Monterey as being ac- 

 ceptable only with "due caution." A large series of comparative mate- 

 rials from both the Atlantic and Pacific Oceans, is needed to solve the 



