THE TERTIARY FORMATION. 39 



tubercles, varying (like the spines of the ventral ridge and the extremities) in their 

 development in different individuals. 



Dorsal profile sagittate and jagged ; end-view triangular. 



Cythere {Cythereis) horrescens occurs both at Barton and Bracklesham, in the 

 Tertiary clays. According to M. Bosquet, this species and its varieties are found in 

 the " Sables moyens," the " Calcaire grossier," and the " Sables glauconiferes " of 

 France. 



I have found two specimens of this fine species in the sand dredged by Messrs. 

 MacAndrew and Barrett on the Norway Coast. 



No. 4. Cythereis Ceratoptera, Bosquet. Plate IV, fig. 1. 



Cythere Ceratoptera, Bosquet. Mem. Couron. Acad. Belg., xxiv, p. 114, t. 5, fig. 2. 



INCH. 



Length, T 'g Pliocene : Suffolk. 



Upper and Middle Eocene : Belgium and France. 



Carapace sub-oblong, tapering posteriorly ; smooth ; strongly and coarsely spined 

 on the anterior, dorsal, and posterior margins, and along the ventral ridge, which is 

 very much produced. 



Dorsal aspect sagittate, with the edges jagged ; end-view triangular. 



From the Crag of Sutton, Suffolk, where it appears to be rare. Bosquet obtained 

 it in Belgium from the Basele Clay near Rupelmonde, and from the Nucula-bed at 

 Berg, near Klein-Spawen ; and in France from Tertiary sands near Etampes. 



No. 5. Cythereis cornuta, Roemer, sp. Plate IV, fig. 19 ; PI. V, figs. 15 a, \bb. 



Cytherina cornuta, Roemer. Neues Jahrb. f. Min., &c, p. 518, t. 6, fig. 31. 



— Reuss. Verstein. Bohm. Kreid., p. 105, t. 24, fig. 20. 

 Cythere cornuta, Bosquet. Mem. Couron. Acad. Belg., xxiv, p. 117, t. 6, fig. 4. 



— — Reuss. Zeitsch. Deutsch. geol. Ges., vii, p. 282, t. 10, fig. 10. 



— (Cythereis) alata (?), Bosq., Jones, Monog. Entom. Cret., p. 21, t. 5, fig. 14. 



inch. 

 Length, ^V Middle Eocene : England and Europe. 



Cretaceous : England and Europe. 



Carapace sub-oblong ; oblique and somewhat rounded in front ; posterior lobe 

 sub-angular ; extremities denticulate ; surface smooth, occasionally marked with one or 



