SUBTERRANEAN AMPHIPOD STYGONECTES 



19 



be a few more described species from epigean habitats than from 

 subterranean habitats. A number of the ground-water species still 

 retain eyes and pigment, although both of these characters are usually 

 greatly reduced. 



Remarks. — In a recent paper on Stygonectes the rather nebulously 

 defined genus Synpleonia was synonymized with the former (Holsinger, 

 1966). Synpleonia was erected by Creaser (1934) on the basis of a 

 single species, S. clantoni, but was never in my opinion shown to be 

 morphologically distinct from Stygonectes, the latter being the older 

 of the two names in use. 



Table 2. — Comparison of six representative North American genera of the Crangonyx 



section 



Recently, I redefined and gave a rather concise diagnosis of the 

 genus Stygonectes (Holsinger, 1966), but on the basis of the current 

 investigation it is now necessary to give an even more thorough 

 diagnosis as presented above. With the addition of a large number 

 of new species and intensive study of all previously described species 

 it has been mandatory to make several modifications and a few addi- 

 tions. This has been done, however, without appreciably altering or 

 extending the overall limits and concepts I had previously established 

 for this genus. 



Six species groups, including two subgroups, have been erected to 

 receive the 29 presently recognized species of the genus. These groups 

 should not be construed taxonomically as subgenera, however, since 

 they have not been described and delineated with this concept in mind. 

 The major reason for erection of these species groups is largely for the 

 purpose of calling attention to, and placing together in the same group, 

 what appear to be closely allied species within a relatively homogeneous 



