118 REPORT — 1872. 



Lias and Oolite — one being from tlie Inferior Oolite, one from the Upper Lias, and 

 two from the Middle Lias. The little wheel-like plates, which are about the fortieth 

 of an inch in diameter, belong- to Chirodota, and present considerable variety in form, 

 some of them indicating structure not hitherto seen in recent species. They are 

 formed of a number of minute wheel-spokes, varying' from five to thirteen, which 

 start from a central axis and are surrounded on the outside by a wheel-tire ; on 

 the inner edge of some species are a series of very minute teeth extending over 

 the central cavity. One of the prettiest forms is from the Inferior Oolite, which 

 the author did himself the honour to name Chirodota Carpenteri, after the President 

 of the Association, who had done so much for microscopic science. In this species 

 the wheel-tire was divided into a number of sections, giving- it a very ornate 

 appearance. The author concluded by expressing a hope that this interesting class 

 of animals would receive a more systematic study than had hitherto been given to 

 them. 



On the Geolorpj of the Tlmnder Bay and Shahendowan Mining-Districts, on 



the NorlJi Shore of Lake /S'((j)2)'/or. Bif H. Alleyne Nicholson, M.D., D.Sc, 

 F.B.S.E., F.G.S., Professor of Natural History in University Colleye, 

 Toronto. 



In this communication the author gave a short account of the leading geological 

 features of the mining-districts of Thunder Bay and Lake Shabendowan, on the 

 north shore of Lake Superior. After giving an account of the chief points of 

 interest in the physical structure of Thunder Bay, it was shown that the chief 

 metalliferous veins of this region are situated in the group of rocks which are 

 known to Canadian geologists as the " Lower Copper-bearing series." The litho- 

 logical characters of this series were briefly described, and it was shown that the 

 age of the group is probably Lower Silurian. Finally, the author described the 

 leading lodes of the district, and pointed out that it was likely to become one of 

 the richest silver-bearing regions in the North-American continent. 



The Lake Superior gold-districts are situated round Lake Shabendowan and to 

 the N.E. of this, and occupy a lai-ge area of country which is placed about sixty 

 miles from Thunder Ba}', and is reached by "the " lied lliver ronte." The geology 

 of the country intervening between Thunder Bay and Lake Shabendowan was 

 briefly described ; and it was shown that the auriferous veins intersect a vast series 

 of Iluronian slates. These slates are for the most part greenish grey in colour, 

 Eometimes fine-grained, sometimes brecciated, and often glossy and soapy from 

 the presence in them of talc. The slates are interstratified with beds of trap ; and 

 the author drew especial attention to the exceedingly close resemblance which they 

 present to the so-called " Green Slates and Porphyries " of the Lake-district of the 

 Korth of England — a resemblance which is shown, not only in the mineral nature 

 of the rocks, but in the kind of scenery produced by their weathei-ing. The author 

 also expressed I'.is opinion that these Iluronian slates, though generally spoken of 

 simply as " talcoso slates," are truly of the nature of bedded felspathic ashes, and 

 that the talc which they contain is a secondary product developed in them by me- 

 tamorphic action subsequent to their original formation. The gold-bearing veins, 

 finally, were shown to have generally an E. and W. or E.N.E. and W.S.W. direc- 

 tion, conforming to the strilie of the rocks which thej' traverse ; and the ores which 

 they contain were shown to be chiefly auriferous copper-pyrites and free gold, with 

 the occasional occurrence of galena, silver-glance, metallic silver, and iron- 

 pyrites. 



On Ortonia, a neiv Genus of Fossil Tuhicolar Annelides, with Notes on the 

 Genus Tentaculites. By H. Alletne jSTicholson, M.D., D.Sc, F.B.S.E., 



Professor of Naturcd History in University Colleye, Toronto. 



Having carefully examined numerous examples of the genus Tentaculites, Sclilot., 

 the author had arrived at the opinion that fossils of very different zoological affini- 



