410 



Prof. T. Rupert Jones — South African Shells. 



The specimens are brown casts, having the surface concentrically 

 wrinkled, with lines of growth rather numerous, sometimes strong, 

 and often irregular, apparently from pressure on a thin shell. This, 

 if once calcareous, has disappeared, leaving a brown film externally, 

 and a thin dark line, where it has been broken across, in the stone. 

 They remind us, in general appearance, of similar shells in the 

 English Wealden. 



The shape varies from suborbicular to oval, suboval, and trigonal ; 

 some have evidently been shortened and others lengthened by 

 pressure. One specimen has obscure remnants of a hinge, showing 

 traces of cardinal and lateral teeth. 



It occurs to me that these small Bivalves may be conveniently 

 referred to Cycladidce, and probably more nearly allied to Cyrena 

 than to Cyclas. Hence we may provisionally name them Cyrena ? 

 neglecta. 



These two little blocks of Karoo stone were collected by Mr. 

 Bain at the village of Balfour, on the right bank of the Kat River, 

 400 yards north of the Rev. Mr. Thompson's house, and are pre- 

 served in the Museum of the Geological Society, London. 



A portion of one of the blocks from the Kat River, Eastern Province, South Africa, 

 showing four of the small shells and parts and sections of others ; magnified 

 twice the natural size. 



These differ from the four South- African " Cyrena} " (?) figured 

 and described or noticed by D. Sharpe in the Trans. Geol. Soc. 

 ser. 2, vol. vii. pp. 199, 202, and 225, pi. 28, figs. 7, 8, 9, and 13. 

 Tig. 7 (undetermined) is from the same great Karoo formation, 

 further north, at Graaf Reinet ; but figs. 8 and 9 (undetermined), 

 and 13 (Cyrena? Bainii) are from a different series of strata on the 

 Zwartkop River. 



