RECENT BRITISH OSTRACODA. 



437 



Northumberland and Durliam coasts, 25-46 fathoms [G. S. B.) ; Ormeshead and Shetland {Mr. D. 



Robertson) ; Hebrides, 45-60 fathoms [Mr. J. G. Jeffreijs). 

 This is a strictly deep-water species, and, though occurring over a wide range of coast- 

 line, is seldom found in great numbers. The only locality in which I have found it at 

 all common is Bu'terbuy Bay, Ireland, where it is mostly of a deep-brown or slaty-blue 

 colour. 



Genus 7. Xestoleberis, G. O. Sars. 



Shell very smooth and polished, ornamented with small round distant papillae, much 

 lower in front than behind, in the female very tumid behind. Hinge-joint formed by a 

 dentated projecting crest of the left, which is received into an excavation of the right 

 valve. Ventral margin of both valves iucarved in front of the middle. Upper antennae 

 six-jointed, the last four joints successively decreasing in length, and bearing very short 

 simple setae ; lower antennae short, four-jointed, flagellum of moderate length. Mandi- 

 bular palp four-jointed; "branchial appendage small and bearing only two seta)." 

 Maxillae as in the preceding genus. Peet short. Postabdominal lobes bearing two setsd. 

 Eyes distinct. Ova and immature young borne within the shell of the female. 



This genus is chiefly distinguished by the peculiar 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 Eucythere, with which, however, in the character of the hinge- 

 joint and of the surface-markings, it to a great extent agrees. Zenker and Sars agree in 

 stating these animals to be viviparous, a character which I have not myself had an op- 

 portunity of examining. 



1. Xestoleberis aurantia (Baird). (Plate XXVII. jQgs. 34-37, and Plate XXXIX. 

 fig. 6.) 



Cythere aurantia, Baird, Mag. Zool. & Bot. ii. 143, t. v. fig. 26 (1835), and Brit. Entom. p. 171, tab. xxi. 

 fig. 8. 



nitida, Lilljeborg, De Crust, ex. ord. trib. p. 169, tab. xix. figs. 6-7. 



viridis, Zenker, Anat.-syst. Studien iiber die Krebst. p. 86, tab. v. A. 



Xestoleberis nitida, G. O. Sars, loc. cit. p. 67. 



Atlantic type. Distribution : Recent — Norway, Great Britain, Ireland. 



Carapace of the female, seen from the side, subtriangular ; greatest height a little behind 

 the middle, equal to nearly two-thirds of the length. Anterior margin much narrowed, 

 rounded ; posterior very broadly rounded ; superior boldly arched, sloping more steeply 

 in front than behind ; inferior slightly sinuated in front of the middle. Outline, seen 

 from above, ovate, tapering gradually to a point in front, broadly rounded behind ; 

 greatest width behind the middle, equal to half the length. The shell of the male 

 (see fig. 35) differs in being more elongated and scarcely so tumid behind. Shell smooth 

 and polished, bearing very small scattered papillae. Colour deep brownish orange, or 

 sometimes white ; a very conspicuous black or deep-crimson spot in front of the eyes. 

 Second joint of the upper antennae shorter than the three following ; terminal claws of 

 the lower antenna) short, scarcely more than double the length of the last joint ; flagellum 

 stout ; poison-gland very large and deeply coloured. Second joint of the last pair of 



