Section IV., 1899. [ 39 ] • Trans. R. S. C. 



ll,—Studies on Cambrian Faunas, No. 3.— Upper Cambrian Fauna of 

 Mount Stephen, British Columbia.— The Trilobites and Worms. 



By G. F. Matthew, D.Sc, LL.D. 



(Read May 25th, 1899.) 



Through the favour of Byron E. Walker, Esq., manager of the Bank 

 of Commerce, Toronto, I have had placed in my hands for study a 

 collection of slabs and fragments of the shale from the interesting locality 

 on the slope of Mount Stephen, whose fauna was first studied by the late 

 Dr. Carl Eoeminger, and later by Mr. C. D. Walcott, now the Director of 

 the United States Geological Survey, and from which a species of Phyllo- 

 carid was described by Mr. J. F. Whiteaves, palaeontologist of the Cana- 

 dian G-eological Survey, 



The tine condition of preservation in which the fossils of this locality 

 are found, as well as their abundance, makes them available for compari- 

 son to an unusual degree, and permits the elaboration of more complete 

 descriptions of the species than is usually possible with fossils of such 

 antiquity. In some cases the whole body is preserved, and frequently 

 all with the exception of the movable cheeks ; even when the parts are 

 wholly separated, they are so well displayed on the surface of the layers 

 that their relationship to each other can often be readily seen. 



One cause that contributes to this result is that a great many of the 

 species had thin tests so that they were almost completely flattened on 

 the layers when the pressure of a superincumbent mass of mud came to 

 rest upon them. But this cause had its disadvantages as regards the aspect 

 of the fossils, when the layers are split open for examination ; for not 

 only does the imprint of one fossil on another obscure the characters of 

 the latter, but the features that characterize the interior surface of the test 

 become imprinted on the exterior. Thus a marginal fold that was not 

 prominent becomes so in the fossil by pressure, and an eye-lobe that rose 

 gradually from the level of the cheek now appears to rise abruptly and 

 be narrow as compared with its actual breadth in life. Very often too 

 pronounced furrows appear on the glabella which are really due to raised 

 ridges on the interior of the test. In all such cases the fossils are 

 described as they now actually appear. 



The Mount Stephen shale is of a gray, to dark gray colour, and 

 weathers of a pale gray, or brownish-gray tint. It is somewhat calcar- 

 eous and films of calcite found between the lamimc of the rock, sometimes 

 obscure the fossils. Occasional threads or films of pyrites are found. 

 The chiten of the tests is sometimes entirely removed ; and at other times 



