Vol.51.] FRESHWATER LAMELLIBRANCHIATA. 349 



Fig. 11. Anthracomyn arenacea, figured by Dawson as a synonym of the above- 

 mentioned Naiadites arenacea (' Review of the Bivalve Mollusca of the 

 Coal-Fonn. of N. Scotia,' p. 12, fig. 10 J ). 



12. Naiadites ovalis, Dawson (' Acad. Geol.' 2nd and 3rd eds. p. 205, and 



Quart. Journ. Geol. Soc. vol. x. 1854, p. 39, fig. 24). 



13. Anthracomya ovalis, figured by Dawson (' Rev. of the Bivalve Mollusca,' 

 etc. p. 13, fig. 11) as a synonym of the above-mentioned Naiadites 

 ovalis, Dawson. 



14. Naiadites angulata, Dawson, ' Acadian Geology,' 2nd ed. p. 204, fig. 46. 



Discussion. 



The President bore testimony to the value and importance of 

 the work carried on by Prof, and Mme. Amalitsky in describing 

 and figuring the various species of lamellibranchs from the Coal 

 Measures and the Permo-Carbonit'erous strata of Russia and else- 

 where. The present paper dealing with the African species was the 

 result of several months' work on the British Museum Collection and 

 in that of the Geological Society. He trusted that careful attention 

 would be given to the question of synonymy, and pointed to the 

 valuable list drawn up by Mr. E. T. Newton, F.R.S., in the 

 Quarterly Journal for 1894, attached to Dr. Wheelton Hind's 

 paper. 



Prof. H. G. Seelev stated that in St. Petersburg he had gathered 

 from Dr. Karpinsky that the palaeontological evidence was slender 

 for determining the age of the Permian deposit which yields Rhopal- 

 odon and Deuterosaurus. Beneath that deposit there is a bed 

 termed ' Permo-Carboniferous,' which also yields a few anomodont 

 bones. And somewhat higher in the series are fish-remains of 

 the type of Acrolepis, common to Permian and Trias. Many of the 

 bones that he had studied were from a marine bed full of Modiol- 

 opsis Pallasi and a species of Terebratula. 



The superficial resemblance in dentition between the Russian 

 Permian reptiles and those of South Africa was misleading ; for 

 while both belong to the therosuchia, the African theriodontia all 

 have the coronoid process of the dentary bone much elevated, and 

 the hard palate terminates in a transverse edge behind which the 

 palato-nares descend ; while in the Russian deuterosauria the 

 coronoid process is not elevated, and the palato-nares open as ovate 

 vacuities, as in the palate of nothosaurs and plesiosaurs. 



It was therefore remarkable to find that the freshwater shells of 

 the Karoo rocks were determined as identical with those of the 

 Permian of Russia ; notwithstanding the well-known persistence 

 of freshwater shells in geological time, with little change. The 

 Karoo Beds are of immense thickness, and their outcrop covers 

 about 70 miles of breadth. About 20 miles north of the base, 

 following the dip, the one example of shells occurred which was 

 known in the Colony, at the base of beds yielding Pareiasaurus. 

 He thought that all the African beds which contain anomodontia 

 are probably Permian, and the upper beds of the Karoo System 



J Canadian Record of Science, October, 1894. 



