28 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.18 



antennae appear to be slightly longer than normal. The notch between 

 segment 3 and the dorsal crest of pleon segment 4 is not as deep as in 

 males of Ampelisca cristata forma microdentata, new form, and there 

 are 2 lateral crests on pleon segment 2. These forms resemble the "inter- 

 sexes" described by Sexton (1924). 



Distribution: Widely distributed in the Channel Islands and sur- 

 rounding banks, along the coast of southern California, 14 to 57 fms; 

 also found at Farallon Islands, off the coast of central California, 37 

 fms; off Point Pinos, Monterey Bay, 36 fms; Cedros Island, 40 to 41 

 fms; Gulf of California at Angeles Bay and Georges Island, 10 to 32 

 fms; off Rocky Point, Sonora, Mexico, 11 fms; Port Parker, Costa 

 Rica, 5 fms. 



Ampelisca cristata forma microdentata, new form 



Plates 17 and 18 



Description of female: Differing from the typical form by the re- 

 duction in size of the tooth at the lower posterior angle of pleon segment 

 3. 



Male: Probably not fully developed. Antenna 1 reaching well be- 

 yond the end of the peduncle of antenna 2, flagellum broken ; peduncle 

 of antenna 2 somewhat stouter than in female ; setal tufts of peduncles 

 of antenna typically developed : depression between pleon segment 3 and 

 dorsal crest of pleon segment 4 deeper than in female; dorsal crest of 

 segment 4 with a more massive base, becoming laminar only near apex; 

 pleon segments 2 and 3 with a single, weak, dorsal ridge. 



Types: Holotype, AHF no. 408, female, 14 mm; paratypes, 3 fe- 

 males; allotype, male, 9.5 mm. 



Type locality: Station 1169-40, 3^ miles west of Huntington 

 Beach, California, 17 to 18 fms. 



Material examined: Stations 212-34 (1), 218-34 (1), 249-34 (1), 

 259-34 (1), 277-34 (3), 280-34 (1), 281-34 (1), 283-34 (1), 451-35 

 (2), 456-35 (2), 468-35 (1), 472-35 (1), 475-35 (11), 478-35 (1), 

 481-35 (5), 493-36 (1), 506-36 (2), 524-36 (1), 526-36 (1), 555-36 

 (1), 561-36 (1), 562-36 (2), 564-36 (1), 576-36 (1), 607-36 (1), 

 639-37 (2), 643-37 (1), 673-37 (1), 697-37 (3), 701-37 (4), 706-37 

 (4), 732-37 (1), 747-37 (1), 769-38 (18), 770-38 (12), 893-38 (3), 

 930-39 (1), 936-39 (6), 941-39 (2), 964-39 (2), 1003-38 (3), 1031- 

 40 (1), 1078-40 (1), 1087-40 (2), 1096-40 (1), 1123-40 (1), 1142- 

 40 (6), 1143-40 (3), 1160-40 (4), 1168-40 (7), 1169-40 (24), 

 1190-40 (4), 1197-40 (4), 1238-41 (1), 1274-41 (1), 1280-41 (2), 

 1283-41 (1), 1662-48 (2), 1703-49 (1), 1925-49 (12), 2018-51 (5). 



