GAMMARIDEAN AMPHIPODA 201 



Holotype.— AHF No. 613, female, 3.2 mm. 



Type locality. — Station 38-D-2, Cayucos, California, Phyllospadix- 

 pelvetiid grid, July 1, 1961. 



Relationship.- — -Because of its short antennae this species bears 

 close relationship to Parapleustes gracilis Buchholz (see Sexton, 1909) 

 and Paramphithoc brevicornis Sars (1895, pi. 124, fig. 2) but differs 

 from those species by the rectangular, not oval hands of the gnathopods 

 and the shorter and blunter posterior lobes of the fifth articles of the 

 gnathopods. In the shapes of the gnathopods this species approaches 

 P. assimilis (Sars, 1895, pi. 124, fig. 1) but differs by the short anten- 

 nae, uropods, and pereopods, compact body and slightly better 

 developed posterior lobes of article 5 on the gnathopods. 



Another relative, P. oculatus (Holmes, 1908) [see Barnard and 

 Given, 1960, with possible synonyms Paramphithoe pacifica Walker, 

 1898, and Parapleustes johanseni Gurjanova, 1951] is distinguished 

 by its longer antennae, pereopods, uropods, and smaller gnathopods. 

 Possibly P. nautilus is synonymous with P. trianguloculatus (Buly- 

 cheva, 1952). The gnathopods of the two species are similar except 

 for the very narrow, projecting, posterior lobes on the fifth articles 

 of P. trianguloculatus. This is a poor qualitative character because 

 with improper mounting and low-power observation the posterior 

 lobes in the present material appear more slender than they actually 

 are. When carefully traced under high-power microscopy their 

 elongation is observed to be overemphasized by the bases of the dense 

 setal bundles. The eye of P. trianguloculatus is triangular. 



At first sight this species is easily confused with a geographic 

 partner, Parapleustes pugettensis (Dana, see Barnard and Given, 

 1960; Shoemaker, 1964), but its body is more compact, palpably 

 more solid, more opaque and less shiny, its antennae are shorter, its 

 gnathopods are distinctive, all of its appendages are shorter, and it 

 retains for a long time (1+ year) in alcohol (and more vividly in 

 formaldehyde) a pinkness, often splashed with various shades of blue 

 and purple. Its heavier chitinization permits clear observation of its 

 segmental lines in contrast to P. pugettensis. 



Material. — carmel: cobble-pelvetiid surface, scarce (18 per sq. 

 m.); Phyllospadix-pelv etiid grid, abundant (105 per sq. m.); algal 

 holdfasts, rare; coralline algae, rare; tunicates and sponges, rare. 

 cayucos: Phyllospadix-pelvetiid grid, rare (16 per sq. m.). hazard 

 canyon: algal turf on platform, 4th most abundant species (200 



Figure 54. — Parapleustes den, new species, male, 8.0 mm. station 6: a, lateral view; b, 

 accessory flagellum; c, mandible; d, upper lip, ventral edge up; e, lower lip;/, gnathopod 

 1; g, A, gnathopod 2; i, enlargement of posterior edge of article 2 on pereopod 3; ;', telson; 

 k, uropod 3. 



