MARINIE GtAMMARIDEAN AMPHIPODA 13 



Synopiidae). Its presence is of relatively uniform value at the generic 

 level (example of an exception is Bathymedon) and its shape is often 

 of good specific value. 



Gill structures have been used occasionally for specific and generic 

 distinctions but their conditions have been ignored in most Gamma- 

 ridea and require extensive study. Gills are often well known in those 

 genera in which accessory tube-like branchial appendages have been 

 discovered or where the primary gills are extraordinarily plaited or 

 folded. Brood lamellae of the female also have been largely ignored 

 although a great deal of variation occurs in their shape, setosity, and 

 terminal ornamentation of the setae. They and the gills may be of 

 assistance in tracing phylogenetic relationships among families and 

 superfamUies of Gammaridea. Male reproductive appendages gener- 

 ally occur as a small pair of projections on the seventh pereonal 

 sternite; occasionally they are spinose. Other sternal teeth, keels, and 

 flanges appear to be of rare occurrence (e.g., Aoridae, Eophliantidae) . 



Geographic Distribution of Marine Gammaridea 



The distribution of so few species of Gammaridea is well known 

 enough as to offer a precise statement of their geographic distribution, 

 but the distribution of most genera is moderately well outlined be- 

 cause, of course, bits of data afforded by each species are cumulative 

 for genera. 



Genera can be sorted out relatively easily by gross geographic zones 

 because faunistic monographers have concentrated primarily within 

 these zones. Only Sars (1895), Chevreux and Fage (1925), and Schellen- 

 berg (1926a) have written faunistic monographs broadly overlapping 

 two zones. Other large scale papers, seemingly monographic, are but 

 obvious collectors' assemblages. Warm-temperate analyses have suf- 

 fered for the lack of discretion between that zone and either tropics 

 or boreal (= cold-temperate) and I have not taken the time to segre- 

 gate precisely the boundaries between the broad arctic-subarctic 

 regions and cold-temperate in describing the distribution of each 

 species. Arctic Amphipoda of the north polar basin are very poorly 

 known and probably very sparse; most of the northern Siberian, 

 Alaskan, Canadian, Greenlandian, and Norwegian shores are placed 

 in the arctic-subarctic region; Iceland, Kamchatka Peninsula, and 

 Okhotsk Sea are considered as boreal (cold-temperate), and that 

 region extends southward to the Japan Sea, middle California, Cape 

 Hatteras, and the Breton Capes; the warm-temperate includes the 

 southern and Baja Calif ornias, Mediterranean Sea, much of north- 

 west Africa, and the northern Gulf of Mexico; south warm-temperate 



