\ 



THE TERTIARY FORMATION. 35 



Carapace oblong ; obliquely rounded in front, rounded behind ; dorsal and ventral 

 edges nearly straight : surface of valves ornamented with a bold reticulation of large 

 square meshes, the longitudinal parietes being strongly developed ; a somewhat con- 

 centric arrangement of the meshes occurs at the central tubercle or place of the lucid 

 spots. [The markings of the surface are not drawn sufficiently distinct in fig. 17.] 



Dorsal aspect elongate-ovate, with the ends produced and truncate ; end-view 

 broadly sub-ovate. 



When some of the longitudinal parietes of the reticulation are more strongly 

 developed than the others, this form approaches C. plicatula and C. Gracilicosta, Reuss. 



Cythere Angulatopora is not uncommon in the Tertiary sands and Oyster-band of 

 Colwell Bay, Isle of Wight. 



M. Bosquet has obtained this species from the " Calcaire grossier" and "Sables 

 moyens " of France ; and Dr. Reuss's specimens came from the " Calcaire grossier " of 

 Epernay. I have found it also in a Middle Eocene deposit from Ghent, Belgium. 



No. 19. Cythere Macropora, Bosquet. Plate III, figs. 9 a — 9 e. 



Cythere Macropora, Bosquet. Mem. Couron. Acad. Belg., xxiv, p. 97, t. 5, fig. 2. 



INCH. 



Length, -,' T Pliocene: Suffolk. 



Middle Eocene : France. 



Carapace oblong ; slightly tapering and rounded behind ; obliquely rounded in 

 front ; somewhat incurved on the upper and lower borders : valves thick, denticulate at 

 the extremities, most convex posteriorly, anterior portion raised by the great central 

 tubercle ; ventral and dorsal portions sloping suddenly inwards, leaving an oblong 

 superficial plateau, the posterior angles of which are defined by the two posterior 

 tubercles : surface covered by a coarse reticulation of large quadrangular pits, sepa- 

 rated by strong squared parietes ; the pits on the dorsal portion of the plateau forming- 

 two curved longitudinal series, those on the ventral portion arranged in three or four 

 obliquely transverse rows ; the ventral and dorsal slopes also coarsely reticulated. 



Dorsal aspect irregular oblong, with produced ends ; end-view sub-quadrangular. 



The very young form (fig. 9 e) exhibits the three tubercles (central and two 

 posterior) very distinctly. 



Cythere Macropjora is rather rare in the Crag of Sutton and elsewhere in Suffolk. 

 According to M. Bosquet, this species occurs very sparingly in the " Gres de Fontaine- 

 bleau " and the " Sables moyens" of France. 



