70 Annals of the South African Museum. 



Cf. 1847. Pecten subacutus A. d'Orbigny, Pale"ont. Frang., Terr. Cret., 



vol. iii., p. 605, pi. 435, figs. 5-10. 

 1872. Pecten subacutus H. B. Geinitz, Das Elbthalgeb. in 



Sachsen, part i., p. 195, pi. xliv., fig. 5 (Palseonto- 



graphica, vol. xx.). 

 1902. Pecten (Chlamys) subacutus H. Woods, Mon. Cret. Lamell. 



Engl., vol. i., part iv., p. 169, pi. xxxi., figs. 7-9. 



(Palseontographical Society.) 



Descriptive Note. A single specimen sent from the collection of 

 the South African Museum seems to approach very closely to P. sub- 

 acutus. The shell is ovate in outline, prolonged dorsally, with an 

 acute apical angle (about 80). The inflation is slight, with the left 

 valve a little more convex than the right. 



The valves are ornamented by about 22 strong, angular ribs with 

 sharp summits. Near the inferior margin the summits of the ribs 

 are separated from one another by a distance of about 2 mm. On 

 parts of the shell the ribs are studded with numerous blunt, spinose 

 projections. Where the surface is well preserved the ribs and inter- 

 spaces are seen to be ornamented by very delicate, transverse linear 

 markings, most clearly visible in the interspaces. Near the inferior 

 margin these become obscurely developed and are masked by 

 coarser ridges and grooves of accretion. The hinge-line and ears 

 are unfortunately not preserved, but having regard to the other 

 characters there is no reason to suppose that they differed essentially 

 from those of P. subacutus. 



Dimensions. Height (about) 42 mm. ; length 35 mm. 



Occurrence. Marine Beds of Sunday's Eiver (304). 



Remarks. Pecten subacutus is characteristic of the Cenomanian 

 in Europe, but this African shell approaches more closely to it 

 than to any form from the Lower Cretaceous with which I am 

 acquainted. In the imperfect material at disposal, no features 

 are apparent which would justify a definite separation from the 

 European form, yet in the absence of the ears in this specimen 

 and the lack of further comparative material, the question of identity 

 must remain open. 



Pecten urgonensis de Loriol,* common in the Urgonian of Grand 

 Saleve, is a shell of very similar type, so far as can be judged from 

 de Loriol' s description and figures ; but apparently its scaly orna- 

 ments are larger and more prominent, and the surface is perhaps 

 more coarsely ribbed. 



* de Loriol (2), p. 389, pi. C, figs. 25, 26. 



