208 POST-TERTIARY ENTOMOSTRACA. 



1. Bythocythere simplex {Norman). Plate VII, figs. 20, 21. 



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



vol. i, p. 17, pi. V, figs. 1 — 4. 

 1865. Bythocytheee acuminata, G. 0. Sars. Overs. Norg. mar. Ostrac, p. 86. 

 1865. JoNESiA SIMPLEX, Brady. Zool. Trans., vol. v, p. 363, pi. Ivii, figs. 11 a — e. 

 1868. Bythocythebe simplex, Brady. Monog. Rec. Brit. Ostrac, p. 450, pi. 



xxxiii, figs. 23 — 27, pi. xl, fig. 8. 



Carapace, as seen from the side, elongated, fusiform, nearly equal in height throughout, 

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

 evenly rounded, posterior tapering abruptly, and conspicuously acuminate below the 

 middle ; superior margin nearly straight, inferior gently convex in front, produced along 

 the posterior two thirds into a much compressed convex keel, sloping steeply upwards 

 behind. Outline, seen from above, acutely ovate, extremities acuminate ; widest in the 

 middle, where the width is equal to one third of the length. Surface perfectly smooth. 

 Lucid spots about five, parallel, linear, oblong, forming an oval, obliquely set patch near 

 the middle of the valve. 



Length, ^2"nd of an inch. 



This remarkable species is known in a living state in Baffin's Bay, on the coasts of 

 Norway, Scotland, and the north of England, and has a range of depth varying from low- 

 water-mark to about sixty fathoms. 



Distribution. Hecent. — Baffin's Bay, Norway, Great Britain. 



Fossil. — Scotland : Duntroon, Loch Gilp, West Tarbert, Cartsdyke, Paisley, Dalmuir, 

 Govan, Jordan Hill. Ireland : Woodburn. 



2. Bythocythere constricta, G. 0. Sars. Plate XVI, figs. 9, 10. 



1865. Bythocythere constricta, G. 0. Sars. Overs. Norg. Mar. Ostrac, p. 85. 

 — — Brady. Monog. Rec. Brit. Ostrac, p. 451. 



pi. XXXV, figs. 47 — 52. 



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

 exceeding half the length ; anterior extremity obliquely rounded ^ posterior obliquely trun- 

 cate, rounded off" at its upper angle ; superior margin straight ; inferior slightly sinuated 

 near the middle, convex and inclined upwards behind. Outline, as seen from above, 

 lozenge-shaped, distinctly constricted in the middle. Surface of the shell marked with 

 delicate grooves mostly running in a subconcentric manner, but frequently anastomosing, so 



