GAMMAEIDEAN AMPHIPODA 27 



warm and cold-temperate waters, Pt. Conception and the capes of 

 Brittany representing the dividing lines in either case. Mediterranean 

 France has a similar atmospheric climate to that of California south 

 of Pt. Conception and winter marine thermal regimes also are similar. 

 In summer, the temperature of inshore Mediterranean waters is 

 about 5° higher than that of southern California. Despite these 

 similarities the amphipodan fauna of Mediterranean France is con- 

 siderably less diverse than that of California or Atlantic France. 

 Species of the three amphipodan faunas are compared in table 32. 



Many similarities occur between the faunas of Atlantic France and 

 California. Several subcosmopolitan species occur in both places (e.g. 

 Leucothoe spinicarpa, Amphilochus neapolitanus) and a tropical species, 

 Ampithoe ramondi, occurs in the southern half of each area. Both 

 faunas have: a species of Panoploea; several species of Ampelisca, 

 two of which are probably obligatory inhabitants of epifloras in each 

 area; subequal representation of amphilochids, aorids, atylids, cor- 

 ophiids, eophliantids, gammarids (Gammaridae, not Gammarus) , 

 hyalids, isaeids ( = photids), stenothoids, and ischyrocerids. On the 

 other hand there is poor representation of ampithoids and eusirids 

 and a complete absence of anamixids, bateids and pleustids in France. 

 In California the following groups are absent or poorly represented: 

 calliopiids (especially Apherusa), dexaminids, haustoriids (mostly in- 

 habitants of sediments) and especially lysianassids. Possibly some of 

 these groups are interreplaceable ecologically but, with the exception 

 of Enequist's (1950) work, little is known of the ecology of the various 

 families. For instance, eusirids and calliopiids may occupy similar 

 niches (indeed the two families eventually may be amalgamated) and 

 bateids may have requirements similar to those of the above groups; 

 thus, 2 bateids, 2 calliopiids, and 7 eusirids of California may be the 

 ecological equivalents of the 5 calliopiids and 1 eusirid of France. 

 The large number of presumed intertidal French lysianassids may be 

 figment ary because they may have been collected primarily in sub- 

 intertidal depths. Pleustids are numerous in the Californian intertidal 

 and, although they are not reported from the French intertidal, they 

 are frequent in subintertidal collections. Perhaps the most striking 

 impoverishment of the French fauna is the poor representation of the 

 genus Ampithoe; only 2 species occur in France whereas at least 11 

 occur in California. The genus is poorly represented everywhere in 

 the north Atlantic Ocean. 



Endemic genera are more numerous in California than in France. 

 Almost all of the French genera are found in other regions of the world. 

 In contrast, California has the following genera which have not been 

 found in other seas, as yet: Neomegamphopus, Netamelita, Fresnillo, 

 Ocosingo, and Pleusirus. France has 69 genera and California 70, but 



