CYPRIDOPSIS— POTAMOCYPRIS. 



129 



in the middle, height equal to nearly two thirds of the length ; anterior extremity well 

 rounded, posterior also rounded, but more acutely; superior margin boldly arched, inferior 

 slightly sinuated near the middle. Seen from above, broadly ovate, pointed in front, 

 rounded off behind, greatest width situated in the middle, equal to nearly three fourths 

 of the length or more than the greatest height of the shell. Surface of the valves smooth, 

 closely set with small, round, impressed punctures ; ventral surface depressed in the 

 middle. Colour yellowish-brown. Valves subequal, the left rather the larger. 

 Length, ^th of an inch. 

 We have expressed elsewhere (' Ann. and Mag. Nat. Hist.,' vol. vi, loc. cit.) the 

 opinion that this may possibly be only a variety of the common C. vidua. To this opinion 

 we still adhere, though without any greater certainty than previously expressed. In the 

 state here described it is at the least a well-marked variety, which without the interven- 

 tion of intermediate forms would never be suspected of any close relationship to 

 C. vidua. 



Distribution. Becent. — Great Britain, Ireland, Holland. 

 Fossil. — England : Hornsea, Branston Fen. 



2. Cypridopsis ? Newtoni, Brady and Bobertson. Plate II, figs. 20, 21. 



1870. Cypridopsis (?) Newtoni, B. ^ R. Ann. and Mag. Nat. Hist., ser. iv, 



vol. iv, p. 14, pi. vii, figs. 14 — 16. 



Carapace, as seen from the side, reniform, greatest height in the middle and equal 

 to a little more than half the length ; extremities rounded, the anterior being the broader 

 of the two ; superior margin boldly arched, inferior sinuated in the middle. Seen from 

 above, compressed, ovate, acuminate in front, rounded behind ; greatest width situated 

 near the middle, much less than the height. Surface of the shell punctate, and (in recent 

 specimens) covered with numerous depressed hairs. 

 Length, ^th of an inch. 



Distribution. Becent. — East Anglian Pen District. 



Fossil. — England : Whittlesea. 



Genus 3 — Potamocypris, Brady. 



Carapace compressed ; seen from the side, similar to that of Cypridopsis, reniform ; shell 

 calcareous and rather thick, valves unequal, the right much the larger and overlapping 



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