Vol. 59.] PALCEOMUTELA FROM RHODESIA. 287 



Appendix II. 



Notes on some Lamellibranchiate Mollttsca obtained by Mr. Moly- 

 neux from the Sengwe Coalfield. By Wheelton Hind, 

 M.D., B.S., F.R.C.S., F.G.S. 



Four small slabs of sandstone obtained by Mr. Molyneux are 

 covered with imperfectly-preserved bivalve shells, which seem to 

 represent two species. 



Three of these slabs, numbered 7, exhibit numerous specimens 

 of a small oval shell, the largest measuring about 9 millimetres in 

 antero-posterior length. Some examples show the surface-markings 

 or casts left by an impression of the surface, while a few bear 

 traces of the anterior adductor muscle-scar. They all have a 

 markedly Unioniform aspect ; but none appear to exhibit the 

 hinge-plate, which is a very important factor in determining the 

 genus to which they belong. 



Prof. Amalitsky has shown l that in the Permian beds of the 

 Oka-Yolga Basin there occur several genera of Unioniform shells, for 

 the generic determination of which the hinge-characters are essential. 

 The same author has studied the collection of lamellibranchs from 

 the Karoo Formation of South Africa in the possession of the 

 Geological Society, and has recognized several species identical 

 with those from the Permian near Nizhni Novgorod. I have had 

 the privilege of examining Prof. Amalitsky's type-specimens in 

 St. Petersburg, and, in his company, the beds in which they were 

 discovered near Nizhni Novgorod. I have also studied the Bain 

 Collections from South Africa, in the Geological Society's Museum, 

 used by Sharpe. On the whole, my biological results agree with 

 those of Prof. Amalitsky, and I only differ from him on mere ques- 

 tions of nomenclature. I think that the small oval gibbose bivalves 

 discovered by Mr. Molyneux in the Seng we Coalfield should most 

 probably be referred to the group named Palceomutela Keyserlingi by 

 Prof. Amalitsky. This species is probably alluded to by Prof. T. 

 Rupert Jones in Geol. Mag. 1890, p. 558, as Cyrena (!) neglecta. 



The fourth slab, numbered 9, is filled with numerous badly- 

 preserved specimens of a bivalve which is much more transversely 

 elongate than Palceomutela Keyserlingi. The specimens are too much 

 eroded to be named with any degree of accuracy. It may, however, 

 be noted that at Graaf Keinet, shells of the form of P. Keyserlingi 

 are associated with elongate types, which Prof. Amalitsky 2 has 

 recognized as Palceomutela subcastor, P. semilunulata, and P. rliom- 

 boidalis (Sharpe). One of these may be represented by the shell 

 now under discussion. At one corner of the slab I think that I can 

 see a portion of the typical hinge of Palceomutela. 



1 'Ueber die Anthracosien der Permformation Russlands' Palseontographica, 

 vol. xxxix (1892) p. 125. 



2 'Comparison of the Permian Freshwater Lamellibranchiata from Russia 

 with those from the Karoo Formation ' Quart. Journ. Geol. Soc. vol. li (1895) 

 pp. 337-49 & pis. xii-xiii. 



