GAMMARIDEAN AMPHIPODA 29 



Chevalia and Cheiriphotis) , most of the species which are shared with 

 any other well-studied region are those occurring in the Japan-Okhotsk 

 region (with particular emphasis on the genus Ampithoe). Even 

 though the greatest regional dissimilarity may occur between the 

 faunas of California and France and the presently known greatest 

 similarities occur between California and the northwestern Pacific, 

 the fauna of the western Atlantic (including the Caribbean Sea) may 

 prove to be that most congruent with California. The warm-temperate 

 and tropical Amphipoda of the western Atlantic Ocean are poorly 

 known. Only 71 species have been reported from littoral-sublittoral 

 depths of the Caribbean Sea and Gulf of Mexico, but 34 of these also 

 occur in the eastern Pacific Ocean. Some of these pan-American taxa 

 occur as far north as California: Ampithoe pollex, A. longimana, 

 A. valida, Paraphoxus spinosus, Ampelicsa schellenbergi, A. lobata, 

 A. venetiensis. Several pan-boreal or pan-tropical species occur on both 

 shores of the Americas: Leucothoe spinicarpa, Calliopius laeviusculus, 

 Pontogeneia inermis, Jassa jalcata, Ischyrocerus anguipes, Cerapus 

 tubularis, Ericthonius brasiliensis, E. hunteri, Elasmopus rapax, both 

 known species of Parhyale, and Melita appendiculata. Common sub- 

 intertidal pan-American species are Ampelisca cristata, A. compressa, 

 A. romigi, A. paciftca, Paraphoxus floridanus, P. epistomus, and 

 Monoculodes nyei. Various closely related counterparts occur as gem- 

 inate pairs of species or subspecies: Heterophlias seclusus ssp., Leu- 

 cothoides paciftca, and L. pottsi, several bateids and carinobateids, 

 Pontogeneia longleyi and P. fminuta. At least 9 of these pairs have 

 been detected. 



Some of the evidence that the exchange of species has occurred 

 primarily from west to east has been discussed by J. L. Barnard (1958). 

 This evidence is composed in the main of the greater diversity of 

 various genera on the Pacific side than on the Atlantic side of America 

 (for instance, 19 Pacific as against 4 Atlantic species of Paraphoxus) . 

 Thus, it is appropriate to suggest that the Californian fauna may 

 have its strongest affinities with the Caribbean region but inappro- 

 priate to suggest that the Californian fauna originated from Caribbean 

 emigrants. 



The intergeographic relationships and heterogeneity of the Cali- 

 fornian Amphipoda may be described in terms of the worldwide dis- 

 tribution of intertidal genera, as well as by those methods already 

 discussed. Intertidal genera of the northern three fourths of the earth 

 are listed in table 34 with their numbers of species, their occurrence 

 in California and their endemicity to the Californian region. The 

 generic relationships of Californian Amphipoda to those of Antarctic 

 seas are so obviously remote that Antarctic genera are excluded from 

 the discussion; in any case few intertidal records of them are extant. 



