RECENT BRITISH OSTRACODA. 



447 



(leg 



inferior nearly straight. Seen from above, the outline is compressed oval, the s 

 nearly parallel in the middle, extremities evenly tapering ; width equal to Less than half 



the length. Eight valve much overlapping the left. Shell marked with a few large and 



deep polygonal or irregularly rounded excavations, each of which has a small eleval d 

 nodule at the bottom; colour yellowish (« in medio vero colore saturate fusco-violaeeo 

 insignis," Sars). 



Length y^ in. 



Hab. Birterbuy Bay and in shell-sand from Donegal and Roundstonc Baya (G. 8. II) ; Lam] ash, Ber- 



M. Norm 



(Mi 



This is the smallest of the genus, and almost the smallest of British Ostracoda. It is 



ery distinct and well-marked species, havin 



o 



with which, however, it is little likely to be confounded 



pt C. chtlJn 



Genus 9. Cytheropterox, G. 0. Sars. 



Valves unequal and of dissimilar form, the right overlapping the left in the middle of 

 the dorsal margin; surface marked with small round impressed puncta or shallow 

 angular pits, sometimes with elevated ribs; ventral surface expanded laterally into a 

 winged process ; posterior margin produced into an obtuse beak. Hinge-joint composed 

 of two terminal teeth on the right valve, and on the left a median crenulated ridge. 

 Upper antennae shortly setose and composed of five joints, penultimate joint elongated 

 and bearing on the middle of the anterior margin two hairs; lower antennae distinctly 

 five-jointed, flagellum long. Mandibles of moderate size; palp three-jointed, branchial 

 appendage bearing two very small setse. Jaws as in the preceding genus. J Vet long 

 and slender, terminal claw slender. Abdomen ending in a long, narrow process, post- 

 abdominal lobes bearing three short hairs. Copulative organs of the male armed behim 

 with three spiniform processes, one of which is trifurcate. Eyes wanting. 



This genus is easily distinguished by the prominent lateral alae of the shell; the 

 peculiar armature of the male copulative organs is a remarkable characteristic of the 

 internal animal structure. 



1. Cttheropteron subcircinatum, G. 0. Sars. (Plate XXXIV. figs. 39-42.) 



tytheropteron subcircinatum, G. O. Sars, loc. cit. p. 81. 



Very similar to the following species, but smaller ; the lateral ala3 almost semicircularly 

 cwed, and not angular. Carapace, as seen from the side, subovate ; highest in the middle., 

 greatest height equal to more than half the length, obliquely rounded in front ; posterior 

 margin somewhat angularly produced ; superior margin forming a flattened arch ; inferior 

 nearly straight, but encroached upon by the convex margin of the lateral ala. Outline, 

 as seen from above, very broadly ovate, widest in the middle; greatest width equal tc 

 two-thirds of the length, extremities very slightly mucronate. End view triangular, 

 *i*th greater than the height, sides convex, base slightly concave; valves un« mat. 

 Surface of the shell faintly pitted, ventral surface longitudinally grooved and bearing i 



