172 



POST-TERTIARY ENTOMOSTRACA. 



Var. CERATOPTERA (Plate XII, fig. 7). 



This differs from the typical form of the species, only in the greater delicacy of its 

 shell-structure and the more attenuated condition of its spinous armature. Our fossil 

 specimens, of which fig. 7 gives a correct idea, do not exhibit these peculiarities so 

 conspicuously as do recent carapaces dredged in the west of Ireland, or more especially 

 in the Mediterranean and Bay of Biscay ; but between the extreme forms of these latter 

 locahties and the robust strongly armed carapaces of the Dogger bank and still more 

 northern habitats — which we look upon as constituting the typical C. Jonesii — every 

 grade of development may be met with. 



Distribution. Recent. — Norway, Great Britain. — (var. ceraUpterd), Ireland, Bay of 

 Biscay, Levant. 



Fossil. — Ireland : Post-tertiary, Belfast New Docks (var.). England : Pliocene, 

 Suffolk. Belgium and France : Eocene. 



41. Ci THERE (?) SEMiPCNCTATA, Brady. Plate XVI, figs. 11, 12. 



1868. Cytheee (?) SEMIPUNCTATA, 5rac?y. Monog. Rec. Brit. Ostrac, p. 41 1, pi. 



xxix, figs. 33—38. 



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

 height equal to fully half the length, extremities well and evenly rounded ; superior 

 margin very slightly arched ; inferior gently sinuated in the middle. Seen from above, 

 compressed, oblong, width equal to one third of the length, lateral margins nearly 

 parallel, extremities produced and broadly truncate. Shell thick, smooth in front, but 

 behind the middle covered with rounded and rather large impressed puncta. Within 

 the anterior and inferior margins the valves are hollowed out so as to form a wide 

 channel, the margins themselves being thickened and everted. 

 Length, ^th of an inch. 



Distribution. Becent. — Bay of Biscay, England, and Ireland. 



Fossil. — Scotland : Raised-beach, Oban. 



