16 U.S. NIATIONAIj museum bulletin 271 



genera. Even though numerous species of tropical amphipods remain 

 to be described, my experience in sorting through quantities of 

 tropical materials suggests that most of these species will be described 

 in known genera. New genera seem to be confined primarily to 

 inquilinous forms probably associated with the vast numbers of 

 sessile tropical invertebrates. Thus Gammaridea are primarily a 

 cool-water group in terms of generic diversity; this is reflected in 

 their strong penetration of the deep-sea. Their body sizes are very 

 strongly associated with thermal conditions in shallow waters, the 

 larger bodies occurring in colder water. This does not apply to deep- 

 sea benthic Amphipoda, however, for there is strong indication (J. L. 

 Barnard, 1962d) that body size becomes smaller or remains relatively 

 static with increase of bottom depth along a latitudinal line. 



About 40 percent of the 53 families of Gammaridea can be classified 

 as cosmopolitan in distribution but the other 60 percent are moderately 

 to strongly confined to specific regions or thermal zones (see below). 

 They are primarily cold-water oriented, for only 6 families with 21 

 genera and 53 species are confined to warm shallow waters of low 

 latitudes. This seems to confirm the orientation of Gammaridea to 

 cool waters. 



The geographic distribution of noncosmopolitan gammaridean 

 families, or those almost whoUy confined to such classification, are 

 as follows: 



Antarctic-antiboreal: Acanthonotozomatidae, Pagetinidae. 



S. warm-temperate: Ochlesidae. 



Tropical: Anamixidae, Bateidae, Kuriidae, Leucothoidae. 



Boreal: Cressidae, Dogielinotidae, Lafystiidae. 



B ATHTAL : Asty ridae. 



Abyssal: Hyperiopsidae, Lepechinellidae, Vitjazianidae. 



Cold water; bipolar submergents: Atylidae, Eusiridae, Haustoriidae, 

 Lysianassidae, Melphidippidae, Oedicerotidae, Pleustidae, Paramphithoidae, 

 Pardaliscidae, Sebidae, Stegocephalidae, Stilipedidae, Synopiidae, Thaumatel- 

 sonidae. 



Warm water; low latitudes: Phliantidae, Prophliantidae. 



In summary, there is scarcely a coastline where an exploratory 

 taxonomist interested in species diversity cannot make some contribu- 

 tion, as Gurjanova (1962) has so ably shown in her study of boreal- 

 subarctic north Pacific; the taxonomist of western Europe, however, 

 must move into beta-taxonomy and the northwestern Atlantic 

 taxonomist must move in that direction in order to detect the rela- 

 tionships of his fauna to that of western Europe. So also, must the 

 northeast Pacific taxonomist orient himself to the groundwork laid 

 for him in Russian Pacific works. The exploratory taxonomist in- 

 terested in total generic diversity will find the greatest needs for 

 study in all warm-temperate regions, the antiboreal, the tropics, 

 and various islands of low latitudes. 



