203 POST-TERTIARY ENTOMOSTRACA. 



the left valve. Lucid spots usually four, linear oblong, arranged in an obliquely trans- 

 verse row just above the middle of the ventral margin. 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 setae. Jaws as in the preceding genus. Feet 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 behind with three spiniform 

 processes, one of which is trifurcate. Eyes wanting. 



1. Cytheropteron latissimum {Norman). Plate VIII, figs. 19 — 23. 



1865. Cythere latissima, Norman. Nat. Hist. Trans. Northumberland and Durham, 



vol. i, p. 19, pi. vi, figs.5 — 8. Brady, Trans. 

 Zool. Soc, 1866, vol. v, p. 381, pi. Ixii, figs. 

 4 a — e. 



1865. Cytheropteeon convexum, G. O. Sars. Overs. Norg. mar. Ostrac, p. 80. 

 1868. Cytheropteron latissimum, Brady. Monog. Rec. Brit. Ostrac, p. 448, 



pi. xxxiv, figs. 26 — 30. 



Carapace of the female, seen from the side, subrhomboidal, highest in the middle, 

 greatest height equal to two thirds of the length. Anterior margin broadly rounded, 

 posterior produced into a short obtusely rounded median beak ; dorsal margin boldly 

 arched, sloping steeply behind, more gently and with a slight sinuation in front ; ventral 

 somewhat convex, sinuated in front ; alaeform protuberance rounded off in front, obtusely 

 angular behind. Outline, as seen from above, subovate ; greatest width situated behind 

 the middle and equal to two thirds of the length ; extremities acuminate. End-view 

 equilaterally triangular, the sides all convex. Shell of the male somewhat more elongated, 

 the posterior beak obsolete. Surface marked with more or less distinct, subquadrangular 

 pits arranged transversely, and often coalescing, so as to form well-marked sulci ; ventral 

 surface longitudinally furrowed. 



Length, ^rd of an inch. 



There is much variety in the surface-marking of this species, some specimens being 

 distinctly reticulated while others are obscurely rugose, owing to the coalescence of the 

 fossae ; in others, again, as in fig. 23, the transverse furrows become exceedingly deep 

 and well marked. It may be distinguished from C. nodosum (with which alone, amongst 

 fossil species, it is likely to be confounded) by the less angular outline, and the absence of 

 any conspicuous tubercles on the dorsal aspect. In the living state C. latissimum is met 

 with abundantly round the shores of Britain and Norway, in a depth of 10 — 60 fathoms. 



