36 U.S. NATIONAL MUSEUM BULLETIN 260 



Hurley (1963) has also made an important contribution in the synony- 

 mization of several genera in the Lyslanassa complex. J. L, Barnard 

 (1962a) has synonymized several genera with Uristes and perhaps er- 

 roneously, as discussed m sequel, has made Tmetonyx a synonym of 

 '■'■Tryijhosa.'''' 



The systematics of gammaridean families and genera is in no way 

 near stability. Many of the "novelties" discovered in the deep sea in 

 recent years apparently are not primitive but are highly specialized, 

 even though simplified. The origin of these species is of considerable 

 interest and their relationships to shallow-water faunas of polar re- 

 gions or of low latitudes must be determined. In view of the under- 

 developed state of gammaridean systematics it is prudent to conserve 

 as many generic names as possible and not to discard them without 

 good cause. It might be better to erect new generic names for the 

 "novelties" rather than to tinker unceasingly with generic diagnoses in 

 order to admit unusual species. 



Many of the deep-sea lysianassids, which are difficult to classify, 

 have affinities with Hippomedon Boeck, Schisturella Norman, '■'•Try- 

 'phoscC auct., and Uristes Dana. Hurley (1963) has proposed two 

 subfamilies in the Lysianassidae, the Lysianassinae and the Uristi- 

 dinae. They include only a portion of the genera belonging to the 

 Lysianassidae, but the genera listed above and those discussed in 

 pages to follow presumably belong to Uristidinae. To avoid any im- 

 plications that the genera discussed below represent all members of 

 the Uristidinae, they are arranged into a hippomedon group, diagnosed 

 in sequel. The major hippomedon group is then divided into a hippo- 

 medon section and a tryphosa section for the purpose of discussing 

 affinities of those deep-sea species that have been difficult to classify. 



The hippomedon group 



Diagnosis. — Lysianassidae with mandibular cutting edge untoothed 

 in middle, mandibular molar well developed, either strongly ridged or 

 densely setulose, occasionally nearly smooth but remaining cuboidal 

 and not becoming laminate or conical, palp attached level with molar ; 

 upper lip and epistome distinctly separated by a notch, incision or 

 chitmous fold; mouthpart field with quadrate outline from lateral 

 view ; palp of maxilla 1 biarticulate, inner lobe with 1 and 2 nonf al- 

 cate setae; maxilla 2 with slender, apposed lobes, terminally setose, 

 occasionally medial edge of medial lobe setose but medial lobe never 

 pointing medially and never armed with large setae as in Arlstias 

 Boeck; maxillipedal palp 4-articulate, article 4 not vestigial, inner 

 and outer plates well developed; gnathopod 1 distmctly subchelate, 

 often minutely, palm oblique or transverse, never grossly chelate ; coxa 



