38 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.18 



Peraeopod 5 very stout; posterior lobe of article 2 large, inferior 

 edge obliquely rounded, extending downward to middle of article 4; 

 articles 3 and 4 subequal in length, article 4 with a massive, posterior, 

 setose lobe ; article 5 subequal in length to 4 ; article 6 broadly expanded, 

 longer than article 5 ; article 7 rather slender, short. 



Uropod 1 almost extending to end of uropod 2 ; rami almost as long 

 as the rather stout peduncle ; outer ramus unarmed, inner ramus with a 

 few spinules on both edges. 



Uropod 2 : outer ramus a little shorter than inner, both much shorter 

 than peduncle; upper edge of outer ramus lined with spinules; both 

 edges of inner ramus spinulose; upper outer edge of peduncle with sev- 

 eral spinules. 



Uropod 3 : rami slender, lanceolate, sparsely setose ; see figure. 



Telson rather slender, apices rounded, each armed medially with a 

 stout spine and a setule ; dorsal surface of each lobe with 2 stout spines. 



Urosome reduced in size. 



Pleon segment 3 : posterior edge nearly straight, posterolateral corner 

 produced into a very large, massive tooth. 



Pleon segment 4: dorsal surface raised into a weakly saddle-shaped 

 process, the posterior edge of which is vertical. 



Pleon segment 6 : lateral ridges weak. 



Description of male: A single male, 6.5 mm in length, from Station 

 1390-41, was found. The setal tufts on the antennae very slightly de- 

 veloped, antenna 2 as long as body, antenna 1 reaching to end of pe- 

 duncle of antenna 2, article 1 of peduncle of antenna 1 very stout, large ; 

 carina of pleon segment 4 slightly more produced than in female. 



Type: Holotype, AHF no. 3910, ovigerous female, 5.6 mm. 



Type locality: Station 936-39, Port Parker, Costa Rica, 5 to 10 fms. 



Material examined: Stations 476-35 (4), 541-36 (1), 701-37 (1), 

 936-39 (1), 1390-41 (1), 1412-41 (1), 1418-41 (1). 



Remarks: This species shows some resemblance to Ampelisca bouvieri 

 Chevreux (1913) but differs in the shape of peraeopod 5, the shorter 

 first antenna, the less strongly produced tooth of pleon segment 3, and 

 the shape of pleon segment 4. 



Distribution: Known from Salinas Bay and Port Parker, Costa 

 Rica, 5 to 10 fms; Gulf of California at Puerto Refugio, Angel de la 

 Guardia Island and Angeles Bay, 32 to 60 fms; Channel Islands, off 

 the coast of southern California, 41 to 47 fms. 



