CYTHEREIS. 175 



1. CYTHEREIS WHITEII. Tab. XX, figs. 3, 3 a* 



Shell oblong, flat, thin, somewhat narrower at one end 

 than at the other. Larger extremity rounded ; the nar- 

 rower extremity somewhat truncated and strongly toothed. 

 The anterior margin and rounded extremity are crenulated 

 throughout the whole of their length, and have placed 

 above them a sort of shelf or pinched-up fold, which runs 

 parallel with the margin, and which is strongly serrated. A 

 sharp crest, which is crenulated, runs along the centre of the 

 valve. The posterior margin is nearly straight and smooth. 



This species is remarkably handsome, and approaches 

 near the Cypridlna serndata of Bosquet (Entomost. de 

 la Craie de Maestricht, t. iv, f. 2, a, d], but is distin- 

 guished from it by being shorter and broader, and by the 

 margin being continued straight to the end, and not in- 

 terrupted and toothed, as in that species. 



Hab. Torquay, in sand ; W. C. Williamson, Esq. 

 Tenby, in sand ; T. Rupert Jones, Esq. 



2. CYTHEREIS JONESII. Tab. XX, fig. l.f 



Shell thick, oblong oval, rather broader at one extre- 

 mity ; the narrower end flattened, with seven strong teeth 

 projecting from the edge, the outer teeth on each side 

 being the strongest ; the broader extremity rounded and 

 convex. The centre of the shell is plane and smooth, and 

 round the whole circumference there is a raised border or 

 narrow plate, which is perforated at frequent intervals by 

 open loop-holes. 



This species approaches the Cytlierina coronata of 

 Roemer (vide Jahrbuch, 1833, t. vi, f. 30) in structure, 

 but differs totally in form, and in having the strong teeth 

 at narrow extremity. 



Hab. Isle of Skye, in sand ; W. C. Williamson, Esq. 



* Named after Adam White, Esq., of the British Museum, well known 

 as the able describer of many new species of Crustacea. 



f Named after T. Rupert Jones, Esq., author of the ' Entomostraca of 

 the Cretaceous Formation,' whose attention in forwarding me specimens of 

 Ostracoda for examination I thus gladly acknowledge. 



