RECENT BRITISH OSTRACODA. 



401 



backwards almost in a right line ; inferior deeply sinuated in the middle. Outline, as 

 seen from above, subliexagonal, widest in the middle, sides nearly parallel and tapering 

 equally to each extremity, greatest width equal to half the length. End view subtri- 

 angular, height much greater than the width, prominently keeled. The central portion 

 of the valves is covered with a thick reddish incrustation, and closely and irregularly 

 pitted ; this central elevated portion is surrounded by a broad flattened margin, which is 

 devoid of pittings, but is marked, especially in front, by radiating lines. The two eyes 

 are plainly visible through the shell, forming brilliant black spots. Upper antennae 

 strongly spinous, last joint shorter than the preceding. Flagellum of lower antenna 

 very short, scarcel}^ reaching the middle of the penultimate joint. Mandibular palp 

 four-jointed, armed with three stout curved plumose setse as in C. cdbomaculata &c,, 

 terminal joint slender. Legs short, and nearly equal, terminal claws long and curved ; 

 second joint of last pair not so long as the two following joints, claw not ciliated. Post- 

 abdominal lobes terminating in two ciliated setae. Male unknown. 

 Length 4^2" in. 



Hab. In rock-pools, Clackland Point, Arran, N.B. {Rev. A. M. Norman). 



This is a very interesting species, as combining the outward form of a typical Cythere 

 with the anatomical characters of the group usually classed under Cythereis. The other 

 two intermediate species, C. albomaculata and C. convexa, are somewhat abnormal both 

 in external and internal structure, and might, with some show of reason, have been 

 erected into independent genera between Cythere and Cythereis ; but C. rubida being 

 outwardly a true Cythere, and anatomically a true Cythereis, seems conclusively to prove 

 the expediency of amalgamating the two genera. 



9. Cytheee convexa, Baird. (Plate XXIX. figs. 19-27, and Plate XXXIX. fig. 4.) 



Cythere convexa, Baird, Brit. Entom. p. 174, tab. xxi. fig. 3. 



arborescens, Brady, Ann. & Mag. Nat. Hist. 1865, vol. xvi. pi. ix. figs. 5-8. 



ICypridina cicatricosa, Reuss, Haidinger's Abhandl. Baud iii. (1850) fol. 67, tab. ix. fig. 21. 

 "^Cythere cicatricosa, Bosquet, Entom. fossil, des terr. tertiair. de la France, p. 76, tab. iii. fig. 13. 

 Cythere punctata, Jones, Entom. of Tert. Form. Eng. p. 24, pi. ii. figs, oa-bh. 



British type. Distribution : Recent — Great Britain, Ireland, Bay of Biscay, Levant. Fossil — Glacial 

 clay and raised beaches, England, Scotland, and Ireland ; crag, England ; and tertiary, Germany and 

 Sicily. 



SheU rounded, convex, beaked behind, slightly keeled in front and below ; greatest 

 height in the middle, equal to about two-thirds of the length ; the left valve much larger 

 than the right, and overlapping considerably on the dorsum. Seen from the side, the 

 anterior margin is rounded, posterior beaked, and expanded below the beak into three or 

 four squamous spines (figs. 19, 25, 27). Ventral margin slightly convex, sinuated at the 

 anterior third, and curved upwards behind, where it also frequently bears one or two 

 sj)ines, which project downwards. Dorsal margin boldly arched, highest in the middle. 

 End view oval, tumid, widest in the middle, pointed above and below. Outline, as seen 

 from above, oblong oval, widest in the middle, and tapering equally to each extremity, 

 width equal to half tlie length. The hinge-processes, with the intermediate bar and 



VOL. XXVI. 3 I 



