XESTOLEBERIS— CYTHERURA. 



191 



2. Xestoleberis aurantia [Baird). Plate XVI, figs. 32, 33. 



1835. Cythere aurantia, Baird. Mag. Zool. Bot., ii, 143, pi. v, fig. 26 ; and 



(1850) Brit. Entom., p. 171, pi. xxi, fig. 8. 



1853. — NiTiDA, Lilljeborg. De Crustaceis, p. 169, pi. xix, figs. 6, 7. 



1854. — TiRiDis, Zenker. Anat. Syst. Studien iiber die Krebst., p. 86, pi. v A. 

 1865. Xestoleberis nitida, G. 0. Sars. Overs. Norg. mar. Ostrac, p. 67. 



1868. — aurantia, Brady. Monog. Brit. Ostrac, p. 437, pi. xxvii, 



figs. 34 — 37 ; pi. xxxix, fig. 6. 



Shell of the female, seen from the side, subtriangular, greatest height situated behind 

 the middle and equal to nearly two thirds of the length. Anterior extremity much 

 narrowed, rounded, posterior very broadly rounded ; superior strongly arched, inferior 

 very slightly sin uated in front of the middle. Seen from above, ovate, acuminate in front, 

 broadly rounded behind, greatest width behind the middle, and equal to half the 

 length. The shell of the is more elongated, and scarcely so tumid behind. Shell 

 smooth and ornamented with minute and distant circula papillae ; there is usually 

 (even in fossil specimens) a dark-coloured spot on each valve near the position of the 

 eyes. 



Length, ^g-th of an inch. 

 Distribution. Becent. — Holland, Great Britain, Ireland. 

 Fossil. — Scotland : Raised beach at Cumbrae. South Wales : New Dock-basin at 

 Cardiff. Ireland : New Docks at Belfast. Norway. 



Genus 8 — Cytherura, G. 0. Sars. 



A^'alves unequal and dissimilar in form, the right more or less overlapping the left on 

 the dorsal margin ; stirface reticulated, punctated, deeply excavated, or bearing irregu- 

 larly disposed ribs or protuberances, mostly marked with a central areola of darker colour 

 than the rest of the shell. Carapace oblong or subtriangular, the posterior extremity 

 produced into a more or less prominent beak. Hinge-processes mostly obsolete. Supe- 

 rior antennse shortly setose, six-jointed, gradually tapering ; second joint bearing a rather 

 long seta on the middle of the posterior margin ; inferior antennae five-jointed, terminal 

 claws short ; flagellum long, triarticulate. Mandibles robust, with very blunt teeth, "palp 

 three-jointed, branchial appendage small, and bearing only two recurved setse." Terminal 



