POST-TERTIARY ENTOMOSTRACA. 



on the dorsal and middle of the ventral margin ; dorsal margin of the left valve some- 

 what flattened, that of the right boldly arched, hingement simple. Limbs short and 

 stout, superior antennae six-jointed, shortly setose, inferior altogether destitute of 

 swimming setae ; first and second feet as in Cypris ; abdomen rudimentary. 



In the living state this genus occurs exclusively in rivers or estuaries within a very 

 short distance of the sea ; very occasionally in the sea itself, in which case it has probably 

 been washed down from freshwater. 



PoTAMOCYPRis FULVA, Brady. Plate I, figs. 20 — 24. 



1868. Bairdia fulva. Brad]). Monog. Recent Brit. Ostr., p. 474, pi. xxviii, fig. 21. 



1869. — — Bradrj and Robertson. Ann. and Mag. Nat. Hist., ser. iv, 



vol. iii, p. 365, pi. xviii, figs. 1 — 4. 

 18/0. PoTAMOCYPRis FULVA, Nat. Hist. Trans. Northumberland and Duiliam, 



vol. iii, p. 366, pi. xiv, fig. 4. 



Carapace, as seen from the side, compressed, angularly reniforra, higher in front than 

 behind, greatest height situated in front of the middle and equal to more than half the 

 length J anterior extremity well rounded, posterior narrowed, rounded below and sloping 

 steeply above the middle ; superior margin arched, almost gibbous at its highest point, 

 whence it slopes with a gentle curve backwards, and more steeply towards the front ; 

 inferior margin distinctly sinuated in the middle. Seen from above, much compressed, 

 ovate, extremities acutely pointed, greatest width situated in the middle, and not much 

 exceeding one third of the length. Valves very unequal, the right being much the larger, 

 and overlapping the left both on the dorsal and ventral margins ; the left valve is thus 

 much narrower as well as more angular in outline, having its ventral margin more deeply 

 sinuated, and the supero-posteal angle more distinctly marked. Shell-structure rather 

 thick. Surface more or less densely and minutely punctate. Colour (of fossil specimens) 

 yellowish-brown. 



Length, of an inch. 



Distribution. Becent. — Great Britain and Ireland. 



Fossil. — Scotland : Dalmuir. 



Genus 4 — Paracypris, G. 0. Sars. 



Shell smooth, compact, higher in front than behind. Upper antennae shortly 

 setiferous ; lower strongly clawed, and bearing on the antepenultimate joint a pedicillated 



