190 



POST-TERTIARY ENTOMOSTRACA. 



only two setae." Maxillae as in the preceding genus. Feet short. Postabdominal lobes 

 bearing two setae. Eyes distinct. Ova and immature young borne within the shell of 

 the female. 



This genus is chiefly distinguished by the pecuHar form of the carapace, which is very 

 low and pointed in front, elevated and tumid behind, in these respects offering a direct 

 contrast to the genus Eucijtliere, with which, however, in the character of the hinge-joint 

 and of the surface-markings, it to a great extent agrees. 



1. Xestoleberis depressa, G. 0. Sars. Plate VII, figs. l;3 — 19. 



1865. Xestoleberis depressa, G. O. Sars. Overs. Norg. mar. Ostrac, p. 68. 

 1868. — — Brady. Monog. Rec. Brit. Ostrac, p. 438, pi. xxvii, 



figs. 27—33. 



1850. ? Cythekina tumida, Reuss. Foss. Entom. Oesierr. Tert. Beckens, p. 5/, 



pi. viii, fig. 29. 



1858. ? Cytiieridea tumida, Egger. Ostrak. Miocan-Schiclit. Ortenburg, p. 17, 



pi. ii, fig. 11. 



Carapace of the female, as seen from the side, subsemicircular, highest in the middle ; 

 greatest height equal to more than half the length. Anterior extremity depressed, 

 obliquely rounded, narrowed, and somewhat exserted at its inferior angle, posterior broader 

 and evenly rounded. Superior margin boldly arched, highest in the middle, sloping with 

 a steep curve towards the anterior, and with a bold convexity towards the posterior 

 extremity ; inferior gently sinuated in front of the middle. Outline, as seen from above, 

 broadly ovate, greatest width behind the middle and equal to two thirds of the length ; 

 anterior extremity acutely pointed, posterior broadly rounded. End-view subtriangular, 

 the width considerably greater than the height, lateral and ventral margins all gently 

 convex. The shell of the male\'& longer in proportion to its height and more depressed in 

 front ; seen from above it is narrower, and has the greatest width in the middle ; the 

 width is greater than the height and the ventral surface is nearly flat. Surface of the 

 shell smooth, polished and often iridescent, bearing numerous very small circular 

 papillae. 



Length, 43th of an inch. 

 This is one of the most abundant and widely distributed of recent marine species, 

 being found all round the British Islands and on the Scandinavian coast, mostly in depths 

 of 2—30 fathoms. 



Distribution. Recent. —(jxt?X Britain, Ireland, Norway, Spitzbergen, Gulf of St. 

 Lawrence. 



Possil. — Scotland : Loch Gilp, Paisley, Wick, West Tarbert, Raised beach at Oban. 

 Ireland ; New Docks at Belfast. Norway and Canada. 



