GAMMARIDEAN AMPHIPODA 25 



by tropical faunas of the Gulf of Californian and Panamic provinces. 

 Probably all of the following species are confined northward of the 

 tropical boundary: Aoroides columbiae, Ampithoe humeralis, A. 

 lacertosa, A. lindbergi, Cymadusa uncinata, Eurystheus thompsoni, 

 and Parapleustes pugettensis. Other species that may be in this cate- 

 gory are those occurring as far north as Puget Sound, for example: 

 Maera simile, Melita sulca, Photis brevipes, and P. bifurcata. Most 

 of the remaining ubiquitous Californian species are known to or are 

 presumed to occur well into tropical latitudes although some inhabit 

 only subintertidal depths. 



The nearly equal distribution of the fauna among ubiquitous, 

 northern, southern, and presumed endemic species is not surprising 

 in view of the transition from cold- to warm-temperate environments 

 in the region. Those facts supporting the view that Pt. Conception 

 represents a boundary between provinces (table 28) are as follows: 

 the absence, rarity, submergence, or occurrence in special environments 

 (lagoons with extreme thermal ranges) of numerous northern species 

 south of Pt. Conception; the same factors applying in reverse to 

 southern species north of Pt. Conception. 



Relationships to faunas of other seas. — Few surveys of inter- 

 tidal Amphipoda comparable to that being reported upon have been 

 made in other parts of the world. Indeed, Amphipoda of the sub- 

 intertidal benthos appear to have been studied more thoroughly than 

 those of the intertidal zone. For instance, Sars' (1895) Amphipoda 

 of Norway was based primarily on dredged samples; perhaps this 

 reflected the problem of reaching intertidal localities on a rugged 

 coastline by land transport. Even the early work of Bate and West- 

 wood (1863) was based primarily on dredgings made in Plymouth 

 Sound. Many of the records of European Amphipoda published in 

 the 19th and early 20th centuries were imprecise as to habitat. The 

 writer, to assemble the data presented in tables 31-33, has selected 

 information for the British Isles from the "Plymouth Marine Fauna, 

 1957" and from the faunal list of the Isle of Man prepared by Bruce, 

 Colman, and Jones (1963). Some species included in those compila- 

 tions have been omitted from present consideration owing to impre- 

 cision as to habitat. The faunal extract of French Mediterranean 

 and Atlantic shores is based on Chevreux and Fage (1925) and a 

 conservative approach again has been necessary because of impre- 

 cision as to the intertidal occurrences of several species. Details of 

 the Magellanic fauna have been taken from the compilation published 

 by Schellenberg (1931) with the understanding that his term "littoral" 

 includes primarily sublittoral species. The writer has amalgamated 

 Gurjanova's (1951) records of Amphipoda from the Okhotsk Sea 

 and Japan Sea but has omitted insular Japanese records in order to 



