16 



Annals of the South African Museum. 



The dorsal valve is oval, slightly convex, with the umbo near the 

 margin. The internal margin is ornamented with ridges. From 

 the median septum one or sometimes more branches come off on 

 each side. 



Several examples of this species were found by Mr. Lang when 

 searching for Polyzoa in the broken-up rock. 



LAMELLIBEANCHIA. 



OSTREA, Sp. 



A small specimen of part of a left valve is probably an example 

 of 0. vesicularis, Lamarck.* That species occurs in the Ariyakir 

 Group of Southern India, and is widely distributed in deposits of 

 Senonian age. 



Some other examples of Ostrea, but not sufficiently perfect for 

 specific determination, have been found. 



C 



FIG. 3. Oxtrea (Exoyyra'), sp. 

 valve. Natural size. 



FIG. 4. Perna, sp. Left valve. In- 

 ternal cast of part near the umbo 

 Eight and of part of the ligamental area. 



Natural size. 



OSTREA (BXOGYRA), sp. 

 Text-figure 3. 



There are two right valves which resemble 0. (Exogyra] Langloisi, 

 Coquand, from the Senonian (Santonian) of Algeria and Tunis. f 



* Coquand, Monogr. du Genre Ostrea (1869), p. 35, pi. xiii. , figs. 2-10. Stoliczka, 

 Cret. Fauna S. India, vol. iii. (1871), p. 465, pi. xlii., figs. 2-4, pi. xliii., fig. 1, pi. 

 xlv., figs. 7-12. Peron, Brachiopodes, etc., de la Tunisie (1893), p. 175. Wanner, 

 Palasontographica, vol. xxx., pt. 2 (1902), p. 119, pi. xvii., figs. 10-12. 



f Peron, op. cit., p. 146, pi. xxiv., figs. 14, 19. 



