RECENT BRITISH OSTRACODA. 407 



almost obsolete in the adult, forming a mere transverse tumid elevation of the valve. 

 The anterior margin is broad, well rounded below, and more gradually curved above, 

 where it terminates in a rounded elevation over the anterior hinge. The posterior 

 margin is narrowed, and rather abruptly angular in the middle. Ventral margin nearly 

 straight, or gently incurved in the middle : dorsal elevated over the anterior hinge, 

 thence sloping in an undulating line to the posterior extremity. Seen from above, the 

 carapace is ovate, broadest behind, width somewhat less than the height ; extremities 

 obtuse, outline very irregularly undulated ; no eye-tubercle. End view irregularly qua- 

 drate, somewhat tajjering above. Hinge-processes of the right valve strongly developed ; 

 of the left obsolete (fig. 29). Surface marked with large and deep pittings, often inter- 

 spersed with much smaller ones, and, in the intervals, bearing elevated papillae. Anterior 

 border mostly fringed with a series of from five to twenty, and the posterior extremity 

 with about six teeth ; but these are often entirely absent. Colour yellowish brown. 

 Limbs deep yellow. Shell of the male much elongated, length more than twice the 

 height, upper margin slightly concave behind the anterior hinge (fig. 30). Upper 

 antennae six-jointed, last joint a little longer than the preceding. Urticating seta very 

 slender. Claw of first foot pectinate on its inner margin. Second joint of last foot 

 rather longer than the united length of the two following joints, terminal claw very long 

 and slender. Male copulative organs produced into a much elongated and slender 

 process in front, the apical portion forming two prolongations, the anterior obtusely 

 hooked, the posterior acuminate. 

 Length -^in. 



Hob. 1-60 fathoms, Hebrides and the Minch, Shetland and Channel Islands {Mr. J. G. Jeffreys) ; Oban, 

 Bute, Campbeltown, and Cumbrae {Mr. D. Robertson) ; Dogger bank, Exmouth, Plymouth, Isle of 

 Skye, and Tobermory {Rev. A. M. Norman) ; Orkney [Mr. C. W. Peach) ; Northumberland and 

 Durham coasts, 20-46 fathoms, and in oyster-ooze from Stranraer and South Wales [G. S. B.); 

 Aberdeenshire coast {Mr. Dawson) ; Roundstone {Dr. Alcock) ; Devonshire coast {Mr. C. S. Bate) ; 

 in shell-sand from Baltimore, Frith of Forth, and Margate {Mr. E. C. Davison). 



The characters upon which I rely to distinguish this fine sj)ecies are the central 

 tubercle, which is never, so far as I know, entirely wanting ; the two posterior tubercles, 

 or, in old specimens, the transverse elevation resulting from their coalescence, which gives 

 to the dorsal view a somewhat cuneate outline ; and the absence mostly of any conspi- 

 cuous tubercle over the anterior hinge, and of any well-defined longitudinal sulcus on the 

 dorsal aspect. But, even thus restricted, there is great variety in the different forms of 

 carapace, as will be sufficiently seen by reference to the figures in Plate XXX. The 

 smooth but prominently tuberculated character of young specimens is shown in 

 figs. 38-39, while the gradual disappearance of the tubercles and consentaneous develop- 

 ment of the minor surface-markings may be traced upwards in figs. 37, 36, 30, 24, and 25 ; 

 finally, fig. 32 shows a still older form, in which the surface-markings have become 

 partially obliterated by calcareous deposit, as has been previously described in the case 

 of other species. 



