RECENT BRITISH OSTRACODA. 



417 



terminates in a conspicuous elevation over the anterior hinge ; posterior margin straight, 

 and much emarginate. The dorsal margin slopes pretty evenly backwards from the 

 anterior hinge ; the ventral margin nearly straight, hut bearing a variable number of 

 regularly set, short, blunt teeth. Outline, as seen from above, somewhat cuneate, 

 suddenly narrowed behind, broadest at the posterior third ; width equal to nearly half 

 the length. End view subquadrangular. The surface of the shell is rugose, and bears 

 three rows of elevated processes, or truncated spines ; one row commences at the anterior 

 hinge, running parallel to and within the anterior and ventral margins nearly as far as 

 the posterior extremity ; a second row runs directly backwards, almost in the median 

 line of the valve ; a third and much less conspicuous row runs transversely, parallel to 

 and just within the posterior margin. Animal unknown. 

 Length ^ in., height yg- in, . 



Hab. " In shell-sand from Tenby Prof. T. Rupert Jones ; and from Torquay, W. C. Williamson, Esq." 

 [Dr. Baird) ; Campbeltown, 10 fathoms [Mr. D. Robertson) . 



31. Cythere antiquata (Baird). (Plate XXX. figs. 17-20.) 

 Cythereis antiquata, Baird, Brit. Entom. p. 176, tab. xx. fig. 2. 



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

 clay and raised beaches, England, Scotland, and Ireland. 



Valves rectangular, quadrilateral ; length equal to twice the height. Anterior border 

 rounded at the angles, and armed below with a series of blunt spines ; posterior margin 

 rectangularly truncate, and bearing below the middle several strong linguiform spines. 

 Dorsal and ventral margins parallel, the latter quite straight, the former cleft into three 

 or four segments with intervening sulci. The carapace, as seen from below, is oblong, 

 with projecting lateral alse, which taper towards the front, but terminate abruptly behind, 

 giving to the whole a somewhat arrow-headed outline. Seen from above, the outline is 

 more irregular. End view subtriangular, deeply emarginate below, each lateral portion 

 with two strongly projecting ridges. The surface of the shell is tuberculate, and bears 

 two conspicuous, sharply defined longitudinal ridges, which terminate abruptly in angular 

 elevations near the posterior extremity of the valve. These ribs are mostly perforated at 

 the* base, the rows of apertures thus produced being very conspicuous on the ventral 

 aspect of the shell (fig. 19). The anterior hinge-tubercle is very large and conspicuous. 

 Left valve larger than the right. Upper antennae five-jointed, last joint long and 

 slender; second joint equal in length to the following two; spines straight, very long 

 and slender. Second joint of lower antennae very short, scarcely half the length of the 

 third joint. Second joint of the last foot equal in length to the following two ; terminal 

 claw very long and slender. Abdominal lobes terminating in a short seta. 



Length 2^3- in., height -5-0 in. . 

 Hab. In depths of 7 to 60 fathoms. Hebrides and the Mincli {Mr. J. G. Jeffreys) ; Tobermory, at roots 

 of Laminaria ; Shetland, Isle of Skye, and Plymouth {Rev. A. M. Norman) ; Aberdeenshire coast {Mr. 

 Dawson) ; Oban, Ormeshead, Cumbrae, and Campbeltown, dredged {Mr. D. Robert.son) ; Birterbuy 

 Bay, dredged, and in oyster-ooze from Stranraer (G. S. B.) ; in shell-sand from Tenby {Prof. T. Rupert 

 Jones), Roundstone {Dr. Alcock), and Cowes {Mr. E. C. Davison) ; off Lewis, 18g miles N.W., 

 591 fathoms {Admiralty soundings) . 

 VOL. XXVI. 3 L 



