Vol.51.] PERMIAN FRESHWATER 1AMELLIBRANCHIATA. 337 



25. A Comparison of the Permian freshwater Lamellibranchiata 

 from Russia with those from the Karoo System of South Africa. 

 By Dr. Wladimir Amalitsky, Professor of Geology and Palaeon- 

 tology in the University of Warsaw. (Communicated by Dr. 

 Henry Woodward, P.R.S., P.G.S. Read April 3rd, 1895.) 



[Plates XII. & XIIL] 



Introduction. 



Some palaeontologists, such as Owen ' (1876), Twelvetrees 2 (1880), 

 Trautschold 3 (1881), and others, have pointed out the resemblance 

 which exists between the reptilian fauna of Perm, in Russia, and 

 that of the Karoo formation of South Africa. This similarity was 

 based on the fact that the reptiles of Perm described as Rho- 

 palodon, Fisch., Brithopus, Kut., Orthopus, Kut., Deuterosaurus, 

 Eichw., Cliorhizodon, Tul., Oudenodon, Traut., and others were 

 referred to the Theriodontia, a group represented in the Karoo Series 

 of South Africa. The Russian Permian reptiles referred to have been 

 recently studied by Seeley, 4 who has come to the conclusion that they 

 are closely allied to the South African types, but cannot be placed 

 in the same subordinate groups. This author considers them as a 

 new group, Deuterosauria, exhibiting a strong affinity with both the 

 Placodontia and Theriodontia. 



In 1892/ when describing the lamellibranchiate fauna from the 

 Oka- Volga basin, I pointed out that the typical shells called Palceo- 

 mutela from these deposits were also known from the Karoo Series 

 of South and Central Africa, and had been described as Iridina 

 by Daniel Sharpe 6 and Prof. T. Rupert Jones. 7 At that time, not 

 being in possession of the original forms from the Karoo Series, I, of 

 course, could answer only for the identity of the genus, though, 

 judging from the description given by Daniel Sharpe and Rupert 

 Jones, it was easy to observe that they possessed characters cor- 

 responding to those which I referred to the group of Palceomutela 

 Inostranzewi. I then expressed the opinion that, in consequence of 

 so wide a distribution of Palceomutela, the species of this genus, 



1 Owen, R., ' On Evidences of Theriodonts in Permian Deposits elsewhere 

 than in South Africa,' Quart. Journ. Geol. Soc. vol. xxxii. p. 352. 



2 Twelvetrees, W. H., ' On Theriodont Humeri from Upper Permian in 

 Orenburg,' Bull. Soc. Imp. Nat. Moscou, vol. lv. pt. i. p. 123. 



3 Trautschold, 'Die Reste permischer Reptilien des palseontol. Cabinets d. 

 Univ. Kasan/ Nouv. Mem. Soc. Imp. Nat. Moscou, vol. xv. (1884). 



4 Seeley, H. G., ' Further Evidences of the Skeleton in Deuterosaurus and 

 Bhopalodon from the Permian rocks of Russia,' Phil. Trans. Roy. Soc. vol. 

 clxxxv. (1894) p. 663. 



5 ' Ueber die Anthracosien der Permformation Russlands,' Palseontograpbica, 

 vol. xxxix. p. 209. 



6 Sharpe, D., Trans. Geol. Soc. ser. ii. vol. vii. (1852) p. 226. 



7 Jones, T. R., Geol. Mag. 1890, pp. 410 and 557. 



2b 2 



