or THE ANTWERP CRAG. 405 



developed branchial plate. Terminal lobes of first maxillae short and thick. Branchial 

 plate large and ovate, setose, and with four long deflexed setse at base. Feet elongated, 

 with long, slender claws. Abdomen ending in a large acuminate process ; post-abdo- 

 minal lobes narrow, and bearing three hairs. Eyes mostly absent. 



Btthoctthere coxstricta, Sars. 



Bythocythere constricta, G. O. Sars, Oversigtaf Norges marine Ostrac. p. 85 ; Brady, Monog. Recent 

 Brit. Ostr. p. 451, pi. xxxv. figs. 47-52 ; Brady, Crosskey, and Robertson, Monog. Post-tertiary 

 Entom. Scotland, &c., p. 208, pi. xvi. figs. 9, 10. 



Carapace, as seen from the side, rhomboidal ; height nearly equal throughout, and 

 exceeding half the length ; anterior extremity obliquely rounded ; posterior obliquely 

 truncate, rounded off at its upper angle ; dorsal margin straight, ventral slightly sinuated 

 near the middle, convex and inclined upwards behind. Seen from above, lozenge- shaped, 

 distinctly constricted in the middle. Surface marked with delicate grooves running 

 mostly in a subconcentric manner, but frequently anastomosing so as to form an irre- 

 gular reticulation ; lateral protuberance rounded and not very prominent ; centre of the 

 Talves marked by a deep and wide transverse furrow. Length -^ inch (0-80 millim.). 



One imperfect specimen only was found, in the Sables moyens (zone a Bryozoaires) ; 

 I have therefore been unable to give figures, and have drawn up the description from 

 Scottish Post-tertiary specimens. B. constricta occurs in the living state on the coasts 

 of Norway and the British Islands, usually in depths exceeding 10 fathoms. 



Genus Cttheeideis, Jones. 

 Carapace elongated, subovate, depressed in front ; hinge-margins nearly simple ; 

 shell smooth, punctate, or sometimes grooved ; right valve overlapping the left in the 

 centre of the ventral surface. Superior antennae slender, sparingly setose ; last joint 

 short and bearing six short terminal setae. Mandible slender and curved, with about 

 four very small indistinct teeth : palp 4-jointed, its first joint bearing a conical tooth-like 

 process ; third joint bearing a comb-like series of straight, equal setse, in other respects 

 like that of Cythere. First segment of the maxillae much stouter than the rest. 



Cttheeideis (?) lithodomoides (Bosquet). (Plate LXITI. figs. 2 a-2 d.) 

 Bairdia lithodomoides, Bosquet, Entom. foss. terr. Tertiair. Prance, &c., p. 36, pi. ii. figs. 3a-d. 



Carapace, as seen from the side, oblong ovate, compressed, greatest height situated 

 behind the middle and equal to scarcely half the length, depressed and rounded off in 

 front, wider behind ; dorsal margin gently arched, ventral straight or slightly sinuated. 

 Seen from above, regularly ovate, compressed, widest behind the middle, pointed in front, 

 rounded behind, width equal to the height. End view subcircular. Surface smooth, 

 marked on the anterior portion of the shell with a number of shallow concentric grooves. 

 Length -^ inch (0*98 millim.). 



3i2 



