48 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.18 



Uropod 2 : peduncle not larger than rami ; both edges of inner ramus 

 and inner edge of outer ramus spinulate, apex of outer ramus with a 

 long spine. 



Uropod 3: rami rather slender, lanceolate, not heavily setose (many 

 setae broken off). 



Telson rather broad, lobes notched apically, each notch with 2 or 

 3 setules ; upper surface of each lobe with 3 setules. 



Pleon segment 3 : posterior edge convex, lower posterior angle 

 strongly produced into a large tooth. 



Pleon segment 4 : dorsal posterior surface raised into a large, straight- 

 margined process which almost becomes keel-shaped posteriorly and ends 

 vertically above segment 5. 



Pleon segment 6 with well developed lateral ridges. 



Female: A single female from Station 1321-41 is referred provision- 

 ally here. The specimen resembles the male holotype in the shape of the 

 head, the antennae, peraeopods 1 to 5, the uropods and the telson. It 

 differs from the holotype by the less sharply delimited palm of gnatho- 

 pod 1, and the process of pleon segment 4, which is a low, weakly 

 saddle-shaped structure. These differences fall in the class of secondary 

 sexual characteristics. In addition, the female differs by the shape of 

 pleon segment 3, which has a broadly convex posterior edge and a 

 weak tooth at the posterior lateral corner. It is possible that this female 

 represents a form of this new species similar to that found in Ampelisca 

 cristata Holmes. Until further materials of both sexes are available, it 

 is impossible to justify this solution. 



Types: Holotype, AHF no. 416, male, 8 mm; paratypes, 3 males. 



Type locality: Station 1321-41, 2 miles west of Church Rock, Santa 

 Catalina Island, 45 to 53 fms. 



Material examined: Stations 1055-40 (1), 1321-41 (5). 



Remarks: The male from Station 1055-40 has the dorsal process of 

 pleon segment 4 slightly concave; otherwise it corresponds to the type 

 material. 



This species is closely related to A. pugetica Stimpson but may be 

 distinguished by the shape of gnathopod 1, by the head, and by the dorsal 

 process of pleon segment 4. 



It bears some resemblance to A. macrocephala but differs in the 

 short uropod 1, the large posterior lobe of article 4 of peraeopod 5, and 

 the shape of the head. 



Distribution: Known only from the type locality and north of 

 Granite Island, Angel de la Guardia Island, Gulf of California, 57 fms. 



