222 Canadian Record of Science. 



while the same mode of occurrence Dear the margin of the 

 dyke was found. So also at the High Rock mine appar- 

 ently the most productive ground is that recently worked 

 near the base of the hill, some 400 feet below the workings 

 at the summit. There does not appear therefore to be any 

 diminution of the mineral as we descend so long as the con- 

 ditions for its occurrence continue favorable, and it might 

 upon this theory be generally stated that the only limit in 

 depth at which the mineral may be profitably mined will 

 be fixed by the cost of its extraction. 



Notes on Canadian Fossil Bryozoa l 



By H. M. Ami. 



I. 



Prof. Ulrich is well known to all students of North 

 American palaeozoic palaeontology as being an eminent 

 authority on Bryozoa. Ever since the year 1881 his re- 

 searches and publications on the interesting material which 

 occurs in such abundance in the Cincinnati and allied groups 

 have been received and read with interest, inasmuch as 

 they threw a mass of new light on a humble yet important 

 and but little known class of fossils in America. This 

 last contribution from the pen of Mr. Ulrich is a hand- 

 some and beautiful memoir on the Lower Silurian Bryozoa 

 of the State of Minnesota. Whilst the 237 pages of text 

 and the 28 excellent plates accompanying the same are 

 devoted especially to Minnesota^ Bryozoa, Prof. Ulrich 

 has not deemed it out of place to introduce here and there, 

 for purposes of comparison and observation, certain marked 

 forms coming from other localities. Among the latter may 

 be mentioned a goodly number from Canadian rocks. The 

 purpose of the present notice is to point these out for refer- 

 ence sake as work bearing on the palaeontology of Canada. 



1 The Bryozoa of the Lower Silurian in Minnesota. By E. 0. Uirich- From 

 Vol. III. of the Final Report of the Geological and Natural History Survey of 

 Minnesota. 237 pp. Minneapolis 1893. 



