OF THE ANTWEBP CJiAG. 393 



Ci'THEEE POLYTREMA, nov. sp. (Plate LXVI. figs. 1 65-1 d.) 



Carapace, as seen from the side, oblong, highest in front ; height equal to more than 

 half the length ; anterior extremity broad, well rounded and bordered below the middle 

 with a number of irregularly placed, rather slender, but blunt spines ; posterior extre- 

 mity narrower, scarcely rounded, armed with a few (4-6) downward-pointing long and 

 slender spines ; superior margin sloping, arched and sinuated in front of the middle ; 

 inferior margin nearly straight. The outline viewed dorsally shows a central quadran- 

 gular portion with two broad extremities projecting in the middle line ; width equal to 

 about half the length. The lateral aspect of the valves is marked by three longitudinal 

 sharply-cut ribs, one in the middle, the others just within the superior and inferior 

 margins respectively; the lower is almost straight, the other two are curved; there is 

 also a curved rounded ridge just within and parallel to the anterior margin; the rest of 

 the surface is occupied by large angular excavations arranged in a reticulated manner ; 

 the dorsal and ventral surfaces show also longitudinal ribs, the intervals between which 

 are filled with single rows of angular pits. Length -^ inch (0-98 millim.). 



Cythere polytrema occurs in moderate numbers in the two beds of the vSables infe- 

 rieurs and in the Isocardium-hed of the Sables moyens. Like the preceding, it is an 

 extremely fine and well-marked species ; but the valves seem usually to occur separate. 



Cttheee scabeopapulosa, Jones. (Plate LXVI. figs. 2 a, 2 b.) 

 Cythere scabropapulosa, Jones, Tert. Entom. England, p. 31, pi. v. fig. 16. 



Valves, as seen laterally, oblong, subovate, higher in front than behind ; height quite 

 equal to half the length ; anterior extremity rounded ; posterior narrowed, rounded, and 

 somewhat produced in the middle ; superior margin elevated in front, then sinuated, 

 and distinctly arched behind ; inferior nearly straight for the greater part of its course, 

 curved upwards towards the posterior extremity. Dorsal outline oblong ovate, with 

 jagged or crenate margins. The surface of the shell is closely beset with wart-like 

 tubercles of considerable size ; and the anterior portion has, just within and parallel to 

 its margin a row of bead-like tubercles ; a prominent tubercle over the anterior hinge- 

 joint. Length -^ inch (0-98 millim.). 



One valve only of this species was detected, in the Pectimculus-hed (Sables inferieurs). 

 Professor Jones's specimens were found at Bracklesham in the Middle Eocene. 



Cytheeb dawsoni ■?, Brady and Crosskey. (Plate LXVI. figs. 3 a, 3 b.) 

 Cythere dawsoni, Brady and Crosskey, Geological Magazine, Feb. 1871, vol. viii. pi. ii. figs. 5, 6. 



Carapace, seen from the side, oblong, subquadrate, highest in front. Greatest height 

 equal to one half the length ; anterior extremity well rounded, posterior narrower and 

 not so fully rounded ; dorsal and ventral margins nearly but not quite straight ; the 

 former with a prominence at each end. Outline as seen from above compressed, sub- 



