GAMMARIDEAN AMPHIPODA 155 



red algae below water, rare; Egregia stipe, rare, la jolla: Phyllo- 

 spadix -coralline grid, scarce (63 per sq. m.) ; coralline-red algal mat 

 under Phyllospadix leaves, rare. 



Distribution of Ischyrocerus sp. B. — cayucos: buried cobbles, 

 rare; nodose pink tunicates, moderately abundant; sponge, scarce; 

 Amaroucium sp., abundant, hazard canyon: hydroid Aglaophenia 

 sp., abundant; sponge, abundant; vertical face with sponges, rare. 

 goleta: Phyllospadix-peivetnd grid, abundant (176 per sq. m.) ; 

 Phyllospadix on sand, rare. pt. dume: pelvetiids, rare (9 per sq. m.). 

 pt. fermin: Egregia holdfast, present (Barnard sta. 21). corona 

 del mar: red algae below water, present, la jolla: coralline algae, 

 rare. 



Jassa falcata (Montagu) 



Figures 38, 39 



Podocerus falcatus (Montagu): Sars, 1895, pp. 594-595, pi. 212. 

 Podocerus odontonyx Sars, 1895, pp. 597-598, pi. 213, fig. 2. 



Jassa falcata: Sexton and Reid, 1951, pp. 30-47, pis. 4-30 (with synonymy). — 

 J. L. Barnard, 1959, p. 37. 



Besides several of the numerous forms of this species described 

 by Sexton and Reid the Californian populations are dominated fre- 

 quently by another form. This thin-bodied form is distinct from all 

 others by the shorter anterior coxae, the more slender body, and the 

 poorly retained body pigment which almost completely disappears 

 in alcohol leaving the specimens pale beige instead of purplish-brown. 

 The male first coxae are rounded at their an tero ventral corners and 

 are not pointed as in the typical thick-bodied forms; the second 

 gnathopods are very slender and the posterior tooth of article 6, 

 which varies so much in other forms of the species, is consistently 

 short and armed with 2 stout spines. Article 2 of the accessory flagel- 

 lum, if it is really present, is so short as to be obsolescent. The ven- 

 trodistal end of the first uropodal peduncle lacks any but a vestige 

 of the long process observed in thick-bodied forms. 



Pigment spots are shown on the drawing of the thin-bodied pheno- 

 type; on thick-bodied forms the pigment is diffused except for the 

 bases of the antennae. In earlier times this thin-bodied form would 

 have been described as a distinct species. Nomenclatural distinction, 

 if necessary, should await life history studies because Sexton and 

 Reid found numerous forms developing from a single clutch of eggs. 

 Perhaps in remote geographic areas Jassa falcata has phenotypes 

 not observed on English shores. 



In both normal and thin-bodied phenotypes the inner plate of 

 the maxilliped has a large and a small ventral tooth (outer or below) 



