162 Annals of the South African Museum. 



Thracia robinaldina (d'Orbigny) * is distinguished by its more 

 oblong and less ovate outline, and its more conspicuous umbones. 

 The African shell compares again more closely with the figure of a 

 specimen from the Lower Cretaceous (Boiling Downs Formation) 

 of Queensland, ascribed by Etheridge with some doubt to Thracia 

 primula Hudleston, and figured under the generic name Corimya.\ 

 Less similarity is shown to the specimen originally named Thracia 

 primula, I preserved in the British Museum (Natural History) ; this 

 has greater relative height anteriorly to the umbo, a more curved 

 inferior margin, more strongly compressed valves, a less inflated 

 umbonal region, and less definitely developed posterior carination. 



GENUS GASTEOCH^ENA L. Spengler. 

 GASTROCH^NA DOMINICALIS Sharpe. 



1856. Gastrochcena dominicalis D. Sharpe, Trans. Geol. Soc. Lond., 

 ser. 2, vol. vii., p. 198, pi. xxiii., fig. 4. 



Sharpe described under this name a shell which had bored into 

 a fragment of wood, found on the Sunday's Eiver " near Enon." 

 He also mentions the occurrence of Gastrochcena boring into 

 fragments of wood and Trigonia-shell, also from the Sunday's 

 Kiver. 



Fragments of fossil wood bored by Gastrochcena were collected by 

 Messrs. Eogers and Schwarz from an oyster bed at the base of the 

 cliff below the old school-house at Dunbrodie, Sunday's Eiver (336). 

 The shells are concealed within the short calcareous tubes which 

 line their cavities, and some of these crypts measure about 6 mm. 

 in length. There is no reason to doubt that these specimens repre- 

 sent the same form as that described by Sharpe. This shell was 

 also found boring into lignite in strata of the " Wood Bed " series 

 of the Bezuidenhout's Eiver below Blue Cliff station. 



* d'Orbigny (3), p. 380, pi. 372, figs. 1, 2 (1845). 



f Jack and Etheridge (1), p. 481, pi. 28, fig. 11. 



J Hudleston (1), p. 245, pi. ix., fig. 7. 



Sharpe spoke of this fragment as " bone," but this was corrected on p. 228 

 of Sharpe's paper and by Prof. T. Rupert Jones in an editorial footnote to Tate's 

 paper in 1867, Tate (1), p. 155. 



