22 U.S. NATIONAL MUSEUM BULLETIN 25 8 



The importance of the genus Elasmopus in the Californian inter- 

 tidal should be emphasized. Like so many other amphipods the adult 

 males of Elasmopus are more easily identified than females or juveniles. 

 Small lots of Elasmopus spp., with a single male and numerous other 

 individuals, have been identified only by the male, although the 

 other individuals have been examined cursorily for gross distinctions. 

 Variation in the Elasmopus rapax-complex is of such an order as to 

 confound the taxonomy of the group. Two major open sea morphs 

 are present in California, E.r. serricatus and E.r. mutatus. Apparently 

 their niches are spatially isolated because they do not occur together 

 in samples of Yuth square m. size in the Phyllospadix-ipelvetud zone. 

 The typical subspecies, E.r. rapax, occurs in California only in harbors. 

 Perhaps E. holgurus is a member of the E. rapax complex; again it 

 has a detectable ecological isolation because of its obligatory associa- 

 tion with sponges or tunicates. Elasmopus antennatus is but one 

 character removed from the complex: it lacks palmar ornamentation 

 on male gnathopod 2. A population of E. antennatus from Carmel 

 Point resembles E. rapax serricatus because of its serricate fifth pereo- 

 pod. Serrication of pereopods, being represented otherwise only on 

 E. pectenicrus (pereopod 4), is rare in the genus Elasmopus (35 + 

 species). That two species, heretofore considered distinct, should 

 be shown to have morphs of this kind in a confined area (of perhaps 

 a few square meters), confounds their taxonomic separation. Seasonal 

 phenotypy in amphipodan species has scarcely been studied but it 

 might be used as a point of departure in the elucidation of this problem. 



Intertidal ampeliscids of southern California are primarily of 

 southern affinity. The pan-American Ampelisca schellenbergi reaches 

 its northern limit in southern California and the giant A. venetiensis, 

 of tropical eastern Pacific distribution, is so rare that it has not been 

 collected in this survey even though it was described originally from 

 Venice, California. Ampelisca lobata is a pan-American species of 

 wider distribution than A. schellenbergi; the former occurs as far 

 north as Puget Sound and is, by far, the most frequently occurring 

 intertidal ampeliscid. Both A. lobata and A. schellenbergi presumably 

 have an obligatory association with plant materials whereas most 

 of their congeners build their domiciliary tubes on soft bottoms. 

 Ampelisca is the most diverse gammaridean genus (95+ species). 



At least 10 ampithoids, including a pleonexes and a cymadusa, 

 occur in the Californian intertidal and more may be discovered in 

 northern California. They especially inhabit kelps and may be found 

 to be more diversified subintertidally than heretofore shown. The 

 intertidal collections of the family are difficult to identify specifically 

 because of the rarity of adult males. J. L. Barnard (1965a) gives 

 a few aids in identifying females and juveniles but all problems 



