GAMMARIDEAN AMPHIPODA 157 



not described by earlier workers and the molar of the mandible has 

 a large accessory flake as illustrated herein. 



The third uropod of Jassa falcata is highly characteristic, making 

 it possible to recognize the numerous forms of the species which 

 in juvenile stages are otherwise difficult to separate from the several 

 species of Ischyrocerus. The peduncle and rami are rather short for 

 most ischyrocerids. The inner ramus is flat and bears a single, stout, 

 distal spine; the outer ramus has a long, curved, basally immersed 

 distal spine and 2 sharp, flattened accessory cusps proximal to the 

 spine. The cusps are large and slightly reverted proximally; no known 

 species of Ischyrocerus has this configuration. One of the accessory 

 blades may be smaller than the other and one or two rows of minute 

 setules as well as a small accessory spine may occur in various growth 

 stages. On the thick-bodied form illustrated herein the distal acces- 

 sory blade has become divided, a rare aberrancy. 



Material of thick-bodied form. — carmel: cobble-pelvetiid sur- 

 face, rare (2 per sq. m.); Phyllospadix-pelvetud grid, moderately 

 abundant (35 per sq. m.) ; algal holdfasts, abundant; Macrocystis 

 stipe, rare; tunica tes and sponges, moderately abundant, cayucos: 

 Phyllospadix-pelvetiid grid, abundant (633 per sq. m.) ; buried cobbles, 

 rare; polychaete tubes and sponges, moderately abundant; sponge, 

 rare, hazard canyon: algal turf on platform, moderately abundant 

 (33 per sq. m.) ; Egregia-Laminaria holdfasts, rare; sponges, rare; 

 Egregia holdfasts, moderately abundant; coralline algae, rare, goleia: 

 Phyllospadix-pelvetiid grid, abundant (236 per sq. m.) ; Macrocystis 

 holdfast, rare. pt. dume: short brown algae, rare (11 per sq. m.); 

 Egregia holdfast, rare; sandy social tunicates, rare, corona del mar: 

 Phyllospadix-coraWine grid, rare (10 per sq. m.); loose rocks, scarce; 

 calcareous worm tubes, rare; soft polychaete tubes, rare; Laminaria 

 holdfast, scarce; Phragmatopoma masses, rare to abundant; sponges, 

 abundant; tunicates and polychaete tubes, moderately abundant. 

 la jolla: Phyllospadix-cor&Wine grid, scarce (21 per sq. m.); short- 

 tufted red algae, scarce (22 per sq. m.); sand-inundated algae at 

 high tide line, abundant (1012 per sq. m.); sponge, most abundant 

 species. 



Material of thin-bodied form. — carmel: Phyllospadix roots, 

 rare, cayucos: tidepool of Phyllospadix, scarce; Phyllospadix roots, 

 moderately abundant; Amaroucium sp., scarce, hazard canyon: 



Figure 38. — Jassa falcata (Montagu), thick form, male, 3.9 mm., station 38-A-3: a, 

 lateral view of body and coxae; b, uropod 3; c, d, gnathopods 1, 2; e, f, pereopods 1, 2; 

 £, h, i, uropods 1, 2, 3; ;', maxilliped. Male, 5.0 mm., Horseshoe Cove, Bodega Bay, 

 California, August 10, 1963, coll. R. Sikora: k, uropod 3. 



