OYTHERURA. 



197 



duced behind into a short and obtuse, obliquely truncate, median beak ; superior margin 

 nearly straight ; inferior slightly sinuated ; seen from above, cuneate, greatest width 

 about equal to the height, and situated near the posterior extremity ; acuminate in 

 front, mucronate behind. Shell longitudinally striated and marked, more particularly 

 over the protruberant posterior portion, with a delicately reticulated and punctate 

 pattern ; within the ventral margin on the posterior half of the valve is a sinuous ridge, 

 which terminates behind in an obtusely rounded alseform projection. The male is rather 

 longer and narrower than the female. 

 Length, ^'Oix of an inch. 



Distribution. Recent. — Great Britain, Ireland, Levant. 



Fossil. — Scotland : West Tarbert. 



12. Cytherura Sarsii, Bradi/. Plate XI, figs. 24—27 ; Plate XIII, figs. 18, 19. 



1868. Cytheeuka Sarsii, Bradij. Monog. Rec. Brit. Ostrac, p. 442, pi. xxxii, 



figs. 39—42. 



Carapace, seen from the side, oblong, subquadrangular, nearly equal in height 

 throughout, height scarcely equalling half the length ; anterior extremity rounded ; 

 posterior scarcely produced in the middle ; superior margin nearly straight ; inferior 

 sinuated in the middle ; outline, seen from above, compressed, ovate, widest behind the 

 middle, width considerably less than the height, pointed in front, mucronate behind. 

 End-view broadly ovate, widest in the middle. Surface of the shell smooth or obscurely 

 striated and punctate. 



Length, y^nd of an inch. 



Distribution. Recent. — Scotland. 



Fossil. — Scotland : Duntroon, Loch Gilp, Kyles of Bute, Cumbrae, Cartsdyke, Paisley, 

 Dalmuir, Barrie. Canada. 



13. Cytherura angulata, Brady. Plate XI, figs. 48 — 51 ; Plate XII, fig. 14. 



1868. Cytherura angulata, Brady. Monog. Rec. Brit. Ostrac, p. 440, pi. xxxii, 



figs. 22—25. 



Carapace, as seen from the side, compressed, oblong, greatest height near the middle 

 and equal to about one half of the length ; anterior extremity rounded ; posterior almost 

 rectangular below, and produced above the middle into a large and prominent beak; 



