MARINIB GAMMARIDEAN AMPHIPODA 335 



Cheirimedon jougneri Walker (1903) differs from the type-species 

 of Cheirimedon by the short cleft of the telson and thus resembles some 

 species of "Onisimus" auct. and Paronesimus. Cheirimedon pectini- 

 palma K. H. Barnard (1925) resembles C. latimanus in coxa 1 and 

 mandible but has a poorly cleft telson, and is distinguished from 

 Uristes primarily by the telson. Because these species assigned to 

 Cheirimedon confound its crisp definition and bridge so many other 

 genera it would seem prudent to isolate at least C. latimanus in a genus 

 of its own and assign C. pedinipalma to it provisionally. The latter 

 also has affinities with Hirondellea except in its head. The three species 

 then remaining in Cheirimedon, C. crenatipalmatus , C. jougneri, and 

 C.jemoratus should be examined from time to time in light of a viewpoint 

 that they simply represent minor departures in the evolutionary 

 scheme of certain genera such as Anonyx {C crenatipalmatus and C 

 jemoratus) and "Onisimus" (C. Jougneri) while those species of the new 

 genus, with C latimanus as type, should be considered as possible 

 subgeneric members of Uristes and "Tryphosa." A parallel may be 

 seen in Pseudokoroga rima J. L. Barnard which is simply an Orchomene 

 with enlarged first gnathopod. Perhaps many of the lysianassids with 

 enlarged first gnathopods are the rubble left behind in the differentia- 

 tion of genera, now so remote from their ancestors, that their origins 

 are unrecognizable. 



Cheirimedon is mentioned often in the foregoing keys to Lysianas- 

 sidae because the several species confound the couplets at vital points. 



Chevreuxiella Stephensen 



Chevreuxiella Stephensen, 1915. 



Type-species: C metopoides Stephensen, 1915 (monotypy). 



Accessory flagellum absent; upper lip and epistome not differen- 

 tially produced but both large and helmet-shaped; mandiHe lacking 

 molar and palp; maxilliped of diverging interpretation: possibly 

 composed of small inner and outer plates and an immense opercular 

 palp composed of one article supporting a second minute proximal 

 article; possibly the opercular palp article is the outer plate and 

 the second article is the palp; gnathopod 1 simple, short, article 5 

 longer than 6, article 7 with apical spine; gnathopod 2 simple; coxae 

 1 and 2 much smaller than coxae 3 and 4, coxa 2 partially hidden by 

 3 and coxa 1 partially hidden by 2; coxa 4 large, not posteriorly ex- 

 cavate; uropods 1 and 2 flattened, inner ramus less than half of outer; 

 telson and uropod 3 absent; urosome composed of two segments. 

 Species: 2, Atlantic, antarctic, bathy-abyssopelagic. 



