243 



and polished, inner duplicatures moderately broad and very sharply defined 

 behind; hinge line somewhat flexuose. Eyes well developed. Antennae not 

 much prolonged, the anterior ones with the terminal part 4-articulate and 

 clothed with scattered comparatively short setae, some of them more or less 

 spiniform. Posterior antennas without any dividing suture of the penultimate 

 joint, apical claws rather stout and 2 in number, flagellum very coarse with 

 the knee far below. Mandibles coarsely dentate at the end, palp of moderate 

 size, with the vibratory plate comparatively small, bisetose. Maxillae with the 

 masticatory lobes narrowly produced, palp likewise rather slender, with the 

 distal joint narrow cylindrical in shape, vibratory plate without any deflexed 

 setae at the base. Legs comparatively short and stout. Caudal lamellae with 

 2 short bristles on the tip. Copulative appendages of male well developed, 

 with the terminal part rather narrow, deflexed. 



Remarks. This genus was originally founded by the present author on 

 2 species occurring on the Norwegian coast, one of them having been long 

 ago known and described as a species of the genus Cythere. In recent times 

 a great number of species referable to the present genus have been recorded 

 from different parts of the oceans, all of them rather closely allied to the two 

 at first described. 



134. Xestoleberis aurantia, (Baird). 



(PI. CXI, fig. 1). 

 Cythere aurantia, Baird, British Entomostraca, p. 171, PI. XXI, fig. 8. 



Syn: Cythere nitida, Lilljeborg. 

 ., viridis, Zencker (not O. Fr. Miiller). 



Xestoleberis nitida, G. O. Sars. 



Specific Characters.- -Female. Shell, seen laterally, subtriangular in shape, 

 greatest height somewhat behind the middle and almost attaining -/$ of the 

 length, dorsal margin considerably arched, forming in the middle an abrupt 

 almost angular bend and sloping rather steeply in front, somewhat less so 

 behind, ventral margin almost straight, anterior extremity narrowly rounded, 

 posterior much broader and somewhat obliquely truncated, with the lower 

 corner slightly produced, but obtusely rounded off at the end; seen dorsally, 

 rather regularly ovate in outline, with the greatest width behind the middle 

 and almost attaining 3 /.-, of the length, anterior extremity gradually contracted 

 to an obtuse point, posterior rounded off at the end. Valves moderately firm 

 and semipellucid, with the surface smooth and shining, being only marked by 

 scattered very small knobs, marginal zone narrow and crossed by distinctly 



