SUBTERRANEAN AMPHIPOD STYGONECTES 11 



Throughout this paper a fine line of distinction has not always been 

 drawn between the terms "troglobite" and "phreatobite" (my 

 transliteration of Motas' phreatobie). More often the term "sub- 

 terranean" has been used to designate, without qualification, any 

 species which inhabits subterranean water whether it be from a cave, 

 seep, spring, or well. The term "interstitial" has also been used in 

 reference to certain species and biotopes, but its usage has generally 

 been restricted to noncavernicolous species of the genus; however, 

 until more data are available on the ecology of North American 

 subterranean amphipods, any of the above terms, whether applied 

 to species or biotopes, should be used Avith caution. 



The term "syn topic" as defined and discussed by Rivas (1964) has 

 been adopted and given rather extensive application in this paper. 

 Since "syntopic" is a relatively new and still poorly known term, its 

 definition will be repeated here as given by Rivas (1964, p. 43): 

 ". . . used in reference to two or more related species which occupy 

 the same macrohabitat. These species occur together in the same 

 locality, are observably in close proximity, and could possibly in- 

 terbreed." In my opinion "syntopic" in no way replaces the term 

 "sjmipatric" as defined by Mayr (1963), but it applies to special situa- 

 tions (i.e., two species in the same macrohabitat) only imphed and 

 not specified by the latter term. 



Morphological. — Morphological nomenclature in amphipod tax- 

 onomy has not always been consistent, and a number of terms used to 

 designate specific appendages and other external body parts need 

 clarification. Reference to the more recent monographs on fresh- 

 water amphipod taxonomy by Shoemaker (1942a), Hubricht (1943), 

 and Bousfield (1958) indicate a comparatively wide range in the usage 

 of terminology pertinent to the systematics of this group. 



The following annotated list includes my adopted usage, and in 

 some cases my modifications, of morphological terms found to have 

 been employed rather inconsistently by past workers in the field of 

 fresh-water amphipod systematics: (1) "Pereonites" include the seven 

 thoracic segments of the body, each bearing one pair of pereopods. 

 (2) "Pleonites" consist of the first three abdominal segments, each 

 bearing one pair of pleopods. (3) "Uronites" are the last three 

 abdominal segments, each bearing one pair of uropods. (The six 

 abdominal segments have occasionally been referred to by past 

 workers as pleon segments.) (4) "Pereopods" refer to the seven 

 pairs of thoracic appendages including the first two pairs (gnathopods), 

 which differ from the others by being subchelate. Many of the 

 earlier papers on fresh-water amphipods, including my own (Hol- 

 singer, 1966), have numbered the pereopods separately from the 

 gnathopods (i.e., gnathopods 1 and 2; pereopods 1-5), but I now con- 



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