GAMMARIDEAN AMPHIPODA 159 



base of Phyllospadix leaves, moderately abundant, la jolla: Phyllo- 

 spadix-coTsMme grid, moderately abundant (121 per sq. m.). 



Distribution. — Ubiquitous in all shallow seas except in high 

 polar regions. 



The Genera Microjassa Stebbing and Parajassa Stebbing 



Two species of ischjTocerids from southern California, Microjassa 

 (or "Ischyrocerus") litotes J. L. Barnard (1954c and 1962a) and a 

 new species to be described in sequel, are difficult to classify. Micro- 

 jassa litotes was originally described in Microjassa but later transferred 

 by Barnard (1962a) to Ischyrocerus primarily because coxa 5 is larger 

 than coxa 6; there might have been justification in pointing out the 

 well developed and lanceolate inner plate of maxilla 1 which contrasts 

 with the vestigial plate of the type species, Microjassa cumbrensis 

 (Stebbing), as well as with that of M. macrocoxa Shoemaker (1942b). 

 Nevertheless, M. litotes shares with the type species of Microjassa 

 a similar accessory flagellum (uniarticulate but elongate, in contrast 

 to the genus Ischyrocerus), as well as shortened first and fifth coxae, 

 the fifth not being as strongly shortened as in the type microjassid. 

 The other species of Microjassa to be described is even more difficult 

 to classify because all specimens lack antennae necessary for observa- 

 tion of the accessory flagellum. In other ways the new species is 

 even more aberrant as a microjassid than is M. litotes. Its fifth coxa 

 is as long as the fourth, although the first is shortened in both sexes. 

 Unlike M. litotes, however, it shares an expanded mandibular palp 

 article 3 with M. cumbrensis. 



In order to show the relationships of M. litotes and M. claustris, 

 the genera Parajassa, Microjassa, Ischyrocerus and Jassa are reviewed 

 in the accompanying table (p. 160). One other shallow water ischyro- 

 cerid, Isaeopsis K. H. Barnard is not included because it is easily 

 distinguished from the others by its subchelate pereopods. 



The usefulness of the following characters in a generic classification 

 is nil: mandibular palp article 3, the shape and setosity of maxillipedal 

 palp article 4, and the condition of the inner plate of maxilla 1. Only 

 the type, of the several species of Parajassa, has an expanded third 

 mandibular palp article like that of the type species of Ischyrocerus 

 and Jassa. The type species of Microjassa has the expanded article 

 but 2 of the 4 species do not. The short, blunt maxillipedal palp 

 article 4, with several setae spread on its mediodistal margin, is 

 typical of the type species of all 4 genera (Microjassa being somewhat 

 questionable) but Microjassa macrocoxa has a very distinct situation, 

 a large spine attached to a slender article. Coxa 1 is consistent among 

 the species of the genera as so arranged, being shortened only in 

 Microjassa; coxa 5 is not consistent, being of medium length in M. 



