166 POST-TERTIARY ENTOMOSTRACA. 



33. Cythere emarginata {G. 0. Sars). Plate V, figs. 1 — 6. 



1865. Cythereis emabginata, G. O. Sars. Overs. Norg. mar. Ostrac, p. 38. 

 1868. Cythere — Brady. Monog. Rec. Brit. Ostrac, p. 475. 



Carapace of the female, as seen from the side, subreniform, highest in the middle,, 

 greatest height equal to considerably more than half the length. Anterior extremity 

 obliquely rounded; posterior produced below into a prominent angular lobe; superior 

 margin boldly arched, highest in the middle ; inferior slightly sinuated in front of the 

 middle and curved upwards behind. Outline, as seen from above, compressed, ovate, 

 extremities obtusely mucronate. The right valve very different from the left, higher and 

 more boldly arched, sinuated in front of the anterior hinge ; posterior extremity more 

 deeply emarginate, and more prominent below. The carapace of the male is distinctly 

 quadrangular, its greatest height little exceeding half the length and situated over the 

 anterior hinge ; superior margin only slightly curved ; posterior obliquely truncate. 

 Surface of the valves irregularly sculptured with large angular excavations, which behind 

 terminate abruptly in a transverse ridge a little in front of the posterior margin, and 

 below in a sharply defined ventral rib, which is most strongly developed posteriorly. 

 Hinge-line on the dorsal surface marked by a deep, sharply cut sulcus ; hinge-teeth 

 strongly developed. 



Length, y^th of an inch. 



Distribution. Becent. — Arctic Seas, Norway, Shetland, Iceland, Spitzbergen, 

 Gulf of St. Lawrence. 



Fossil. — England: Bridlington. Scotland: Barrie, Elie, Errol. Ireland: Portrush. 

 Norway and Canada. 



34. Cythere costata, Brady. Plate V, figs. 21 — 24, 



1865. Cythere costata, Brady. Trans. Zool. Soc. vol. v, p. 375, pi. Ix, 



figs. 5 a—f. 

 1869. — — Norman. Brit. Assoc. Report, 1868, p. 290. 



Carapace of the female, as seen from the side, subquadrangular, highest in front of 

 the middle, greatest height equal to somewhat more than half the length. Anterior 

 extremity subtruncate, emarginate above, produced below, and divided into four or five 

 short obtuse teeth ; superior margin arched, gently sinuated in front. Outline, as seen 



