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U.S. NATIONAL MUSEUM BULLETIN 259 



CRANGONYX Section 



A number of investigators have divided the widespread, ecologically 

 and morphologically diverse family Gammaridae into several sections 

 or groups. Schellenberg (1936) distinguished what he called the 

 Crangonyx group and assigned to it 1 5 genera of mostly poorly known, 

 largely subterranean, and almost exclusively fresh-water amphipods. 

 Shoemaker (1942a) went further in giving a more complete diagnosis 

 of the group (which he termed a section); he also wrote a good key 

 to the North American genera of the section and further assigned to 

 it two rare Caribbean island forms plus the North American endemic 

 genus Bactrurus. In a recent treatise on biospeleology, Vandel (1964) 

 briefly discussed the possible origin, affinities, and geographic dis- 

 tribution of the section. 



Table 1. — Representative North American genera of the Crangonyx section of 



Gammaridae 



1 N.A.— North America. 



As indicated earlier, the six representative North American genera 

 of the Crangonyx section (excluding the Caribbean genera) are 

 listed and broken down into numbers of species, respectively, in 

 table 1. At present a total of 17 or 18 recognized genera are assigned 

 to this section, many of which are still poorly known and need 

 redefinition. Although the rather unique. North American endemic 

 genus Allocrangonyx was assigned to the Crangonyx section by both 

 Schellenberg and Shoemaker, in my opinion its affinities with this 

 group are unclear, and the inclusion of this genus in the Crangonyx 



