44 Correspondence — T. C. CantrilL 



called 8p. glabra seem to have been derived from radially costate 

 ancestors. The use of the generic name Martinia for various smooth 

 Spiriferids of the Devonian and Carboniferous thus becomes wholly 

 unjustifiable, as it simply denotes a stage of catagenetic development 

 at which several different stocks of Spirifers arrive. As the outcome 

 of this study the author restricts the genus Spinfer, and allocates 

 several British and foreign species among the genera Fasella, 

 Choristites, Trigonotreta^ Brachythyris, Martinia, and Reticularia. He 

 also gives in an appendix a revised explanation of Davidson's plates 

 xi and xii of the Monograph of Carboniferous Brachiopods. 



COI^.RESI'OlSriDEITCE. 



GLACIATION OF THE USK AND AVYE VALLEYS. 



Sir, — At the meeting of the British Association at York in 1906 

 a paper on the Glaciation of the Usk and Wye Valleys was read by 

 the Kev. W. Lower Carter, and was printed in abstract in the Report 

 (pp. 579-580). An abstract appeared also in the Geological Magazine 

 (for 1906, pp. 521, 522). The author there records several interesting 

 and important glacial phenomena, and it is to be hoped that he will 

 find occasion to continue his researches. There is, however, one point 

 on which it is necessary to register a corrigendum. After speaking of 

 the purely local drift in the region (an Old Red Sandstone district) he 

 calls attention to certain "erratics of volcanic ash and brecciated 

 limestone" (B.A. Report), or "volcanic ash and breccia" (Geol. 

 Mag.), which overlie the local drift; and he supposes them to be 

 derived from distant Ordovician sources. 



A recent visit — unofficial and connected with quite other matters — 

 to the district enables me to say that the erratics of ' volcanic ash ' 

 and ' breccia ' or ' brecciated limestone ' to be seen in the village of 

 Trecastle and on the neighbouring hillsides, and again at Talgarth and 

 along the course of the river Enig above the town are, in fact, boulders 

 of cornstone, of both the conglomeratic and the non-conglomeratic 

 variety ; and that instead of being derived from distant Ordovician 

 sources they are traceable to quite local outcrops of that rock in the 

 valleys in which they occur. Ko doubt ice had much to do with their 

 transport, but their journeys to their present resting-places were not 

 so romantic as a derivation from Ordovician sources would involve. 



T. C. Cantkill. 

 Geological Survey, Jermyn Street, S.W. 

 1th December, 1907. 



RE SPELLING OF PLACE-NAMES. 

 Sir, — The slight demurrer oflPered by your reviewer of the Geological 

 Survey Memoir on " The Geology of the Country around Ammanford " 

 in the November number of this Magazine (1907, p. 515), as to the 

 alteration of the spelling of the place-name ' Llandeilo ' to ' Llandilo,' 

 reminds me of an intention I had of enquiring, through the medium of 

 your Magazine, the views of some of your readers as to the desirability 



