GAMMARIDEAN AMPHIPODA 



61 



gnathopod 2 much broader, more f alconif orm ; pereopods 3-5 slightly 

 longer and more slender and pereopod 3 lacking lateral ridge on article 

 2; pleonal epimeron 2 similar but ventral margin slightly more 

 concave. 



Kelationships. — The similarities of the two populations in terms 

 of general shapes and armaments are striking. For instance, the 

 spines on the outer plate of maxilla 1 are similar, even though complex ; 

 the armaments and shapes of uropod 3 are similar. I have figured the 



Figure 26. — Orchomene pinguis (Boeck), female, 5.0 mm, Santa Monica Bay, Calif., 

 183 m: a, apex of right mandible; b, inner plate of maxilliped; c, outer plate of maxilla 1; 

 d, maxilla 1; e, mandibular palp. Female, 6.8 mm. Woods Hole, Mass., 1875: /-A, pereo- 

 pods 3,4,5. Female, 5.6 mm, Santa Monica Bay: i, maxilla 2; /, maxilliped, inner plate 

 unflattened and setae removed; k, mandible, palpar setae removed. Female, 5.4 mm, 

 Santa Monica Bay: /, lower lip. 



parts from the Californian population and those of the Woods Hole 

 population only where they differ. The posterior edges of the pleonal 

 epimera are minutely but distinctly serrate in specimens from Woods 

 Hole, but the serrations on Californian specimens are extremely weak, 

 especially those on epimeron 3. In both populations the second article 

 of the outer ramus of uropod 3 is longer and more attenuated than that 

 shown by Sars (1895, pi. 24, fig. 2) . 



Coxa 6 was inadequately represented by Sars but is correctly shown 

 by Gurjanova (1962) for populations from the northwestern Pacific 



