236 Annals of the South African Museum. 



Family CYTHERELLID^. 



Genus CYTHERELLA Jones. 

 Cytherella williamsoniana Jones. 



C. iDilliamsoniana Jones, 1849, Mon. Ent. Cret., p. 31, pi. vii., 

 figs. 26a-/z. 



Cy])ridina leioptycha Eeuss, 1851, in Haiclinger's Naturw. Abhandl., 

 vol. iv., pt. i., p. 49, pi. vi., fig. 11. 



Cytherella williamsoniana Jones, Bosquet., 1854, Mem. Comm. 

 geol. Neerlande, vol. ii., p. 62, pi. v., figs. 2a-fZ. Eeuss, 1874, 

 Elbthalgeb., &c., pt. ii., p. 153, pi. xxviii., figs. 9, 10«, h. 

 Marsson, 1880, Mittheil. nat. Ver. Neu-Pommern und Rugen, 

 Jahrgang 12, p. 31, pi. ii., figs. 8a-c. Jones and Hinde, 1890, 

 Mon. Cret. Entom., p. 48, pi. iii., figs. 55-62. Chapman and 

 Sherborn, 1893, Geol. Mag., Decade III., vol. x., p. 347. 

 Chapman, 1898, Ann. Mag. Nat. Hist., ser. 7, vol. ii., p. 344. 

 Egger, 1899, Abhandl. k. bayer. Akad. Wiss., CI. ii., vol. xxi., 

 Abth. 1, p. 188, pi. xxvii., figs. 63-65. 



A single left valve of this peculiar and variable species was found 

 in the East Pondoland material, having a flat surface with the 

 bordering ridge and a sinuous median one, which ends towards the 

 postero-ventral angle in a thickened knob. Our specimen comes 

 nearest to fig. 56 of Jones' and Hinde's monograph. It also bears 

 a certain resemblance to C. jugosa Jones,* which occurred in the 

 Great Oolite of the Richmond Boring. 



As regards geological range, this species first appears in the Gault 

 in zone V at Folkestone, and it ranges upwards to Upper Chalk in 

 England, Ireland, the Isle of Eiigen, and on the Continent of Europe. 



* Quart. Jonrn. Geol. Soc, vol. xl. (1884), p. 773, pi. xxxiv., fig. 44. 



