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very irregular underlying Precambrian surface. The first beds deposited 
on such a floor by an advancing sea would be formed in the hollows between 
the knobs of Precambrian rocks. Towards the north end of the North 
arm observations show that the Precambrian floor had a topographic 
relief of at least 200 to 300 feet at the time it was submerged by the Ordo- 
vician sea. 
At Red Rock point above the sandstones there are 7 feet of heavy 
beds of massive, red, dolomitic limestones which form the capping rock 
of cliffs which owe their persistence to the extremely resistant character 
of these beds. At this point the red beds contain no gypsum and are less 
red in colour than the rocks at Gypsum point. Farther to the north in 
red dolomitic limestones of approximately the same stratigraphic level 
fossils were found. A list is as follows: 
Receptaculites nearest oweni 
Camaroloechia sp. 
Cyrtodonta septentrionis n. sp. 
Conularia esclavensis n. sp. 
Endoceras sp. 
Orthoceras sp. 
Trochoceras sp. 
Some of these fossils were in chert in red limestone and consequently 
in a fine state of preservation. Others were in the limestone itself and in 
many cases the more detailed structure is lacking. 
To the north of the locality where the above fauna was collected the 
rocks become less and less red in colour and more dolomitic in character, 
changing to a yellowish or buff dolomitic limestone. A fauna somewhat 
similar to that found in the red beds occurs at several places, but always 
affords rather poorly preserved material. The fauna is as follows: 
Halysites gracilis 
Palaeofavosites asper 
Camarotoechia sp. 
Lepiaena sp. (peculiar geniculate form, See Plate XIII, figure 3) 
Strophomena sp. 
Strophomena ruga n. sp. 
Other brachiopods whose determination is questionable, but two of 
which probably belong to Rafinesquina. 
Fragmentary Iamellibranchs 
Calymene sp. 
Of the above, Halysites is the most abundant, and as a rule either the 
fossil itself has weathered out leaving the mould, or else the whole has been 
replaced by calcite. However, on detailed examination, it can be definitely 
stated that the cross-section of the individual corallites is quadrangular 
as in H . gracilis . The conclusion, therefore, is that this is the 
Ordovician rather than the Silurian Halysites and this conclusion seems 
to he borne out by the detailed study of the remainder of the fauna. The 
Receptaculites is described and figured in this report. Most of the Silurian 
species so far described are globular forms and such a form was found along 
