Reviews — Geological Survey of Yukon, Canada. 279 



fossils were found in a hard limestone occurring in boulders, and 

 embedded masses in the soft argillaceous clay and shale which is the 

 prevailing rock formation of the neighbourhood. 



The collection is " interesting from the fact that it increases the 

 number of forms from the South Australian rocks in question by five 

 species not hitherto recorded therefrom, and also confirms the 

 identification of two others previously known only from scanty or 

 imperfect material." The genera represented are the following : 

 Aucella, Inoceranms, Haploceras, Anisoceras, Ancyloceras, Crioceras, 

 and Nautilus (Cymatoceras ?). The s^ieGies of Ancyloceras (A. cordy- 

 cepoides) is new. A. H. F. 



X. — Geological Survey of Canada. Eobert Bell, M.D., F.R.S., 

 I.S.O., etc., Acting-Director. Kecent Mineral Discoveries on 

 Windy Arm, Tagish Lake, Yukon. By R. G. McConnell, 

 B.A. 8vo. Ottawa, 1905. 



THESE discoveries proved so interesting that an examination of 

 the district was deemed advisable. Tagish Lake forms part 

 of a chain of long, narrow lakes, originating within the coast range 

 of mountains and extending northward and eastward for a distance of 

 nearly seventy miles. Windy Arm joins Tagish Lake near its head, 

 and extends south for a distance of twelve miles. The Windy Arm 

 mining district consists chiefly of wide valleys intersecting each 

 other, separated by mountain ridges rising from 4,000 to 5,000 feet 

 above the vallej'^s. The mineral area is situated a few miles north 

 of the great granite area of the coast range. 



The rocks out-cropping along the lower part of Windy Arm 

 consist of a wide band of crystalline limestone, followed to the south 

 by hard slates and shales, passing in places into felspathic quartzites. 

 This clastic series is cut off and replaced about five miles above the 

 mouth of the Arm by an ei'uptive rock of a porphyritic character, 

 exposures of which out-crop along the shores of the Arm for 

 a distance of about five miles. The porphyrite is followed southward 

 by strongly cleaved, dark argillites and fine-grained tufaceous 

 sandstones, alternating with bands of conglomerates and limestone. 

 No data sufficient to determine the age of these i-ocks were obtained, 

 though they are less altered than the slates and associated rocks 

 north of the porphyrite area. The porphyritic rock separating the 

 two series of clastic rocks constitutes the principal metalliferous 

 formation of the district. It crosses from Windy Arm to Bennett 

 Lake in a band about four miles in width, and also extends some 

 distance east of Windy Arm. 



A granite area about three miles in width occurs on Lake 

 Bennett, north of the porphyrites and associated rocks. The granite 

 is similar in character to that of the coast range, and probably 

 belongs to the same period of igneous activity. 



The largest and most persistent mineral veins so far discovered 

 occur in the porphyrite area. 



