258 Proceedings of the Royal Physical Society. 



The tusks at their external origin are only If in. apart, 

 but they widen out to nearly a foot at the tips. The right 

 tusk, which is a few inches shorter than the other, has been 

 broken at the tip like the Cambridge specimen, so that the two 

 tusks were probably at one time of equal length. The spiral 

 markings in both tusks go from right to left. A drawing of 

 the skull was exhibited, as also examples of the rudimentary 

 tooth of the narwhal, kindly lent by Mr C. W. Peach. 



IV. Exhihition of Permo-Carboniferoiis Polyzoa, collected hy 



Captain H. W. Feilden, R.A., during the late Arctic 

 Expedition %inder Captain Sir G. Hares. By Egbert 

 Etheridge, Jun., F.G.S. 



Mr Etheridge gave a brief outline of the literature of 

 Arctic Palaeozoic Polyzoa, referring in particular to the works 

 of Count von Keyserling, Mr J. W. Salter, and Dr E. Toula. 

 The more important characters of the species exhibited were 

 dwelt on, and their relation to previously-described forms 

 pointed out. They appeared to be a mixture of Carboni- 

 ferous and Permian representative forms, such for instance as 

 Bamipora ffochstetteri, Toula, previously found only in the 

 Permo-Carboniferous rocks of Spitzbergen, with Polypora 

 grandis, Toula, from the same horizon and locality ; P. biar- 

 mica, V. Keyserling, from Petchora Land and Nova Zembla, 

 with lastly a peculiar and interesting species, Fenestella Arctica, 

 Salter, described in Belcher's " Last of the Arctic Voyages," 

 from Depot Point. Other and less interesting examples were 

 also exhibited and briefly described. The locality is Eeilden 

 Isthmus, lat. 8 2 43 K 



V. On the Occurrence of Prismatic Structure in the Stones of 



Scottish Vitrified Forts. By Professor Duns, D.D., New 

 College. 



It is not intended in this paper to enter at large into ques- 

 tions relative to the age, or the builders of the vitrified forts of 

 Scotland, or even as to their use and the mode and materials 

 of their vitrifaction. These topics, still to a great extent 



