440 
SILURIA. 
[Chap. XYIII. 
ritories (now termed Laurentian) are surmounted by few other deposits on the 
west and north, except by masses of Silurian age, and young Tertiary strata. 
In his graphic description of the structure of Canada, Lyell expressed the same 
opinion. "I seemed/' says he, "to have got back to Norway and Sweden, 
where, as in Canada, gneiss and mica-schist, and occasionally granite, prevail 
over wide areas, while the fossiliferous rocks belong either to the most 
ancient or to the very newest — to the Silurian or to deposits so modern as 
to contain exclusively shells of recent species " *. From the western shore of 
Lake Winnipeg t, a limestone containing gigantic Orthocerata (allied to those 
described by Dr. Bigsby and Mr. Stokes J from the Upper Silurian of Drum- 
mond Island) and the strange fossil named Receptaculites § was traced in hori- 
zontal sheets stretching westwards over four or five degrees of longitude. 
Though this plateau is separated from the Rocky Mountains by a broad belt of 
the Prairies of the Saskatchewan, the bed of that river is full of limestone blocks 
which indicate the persistence of the rock. After crossing Methy Portage, in 
lat. 56f°, Richardson again met with extensive calcareous deposits. The fossils 
which were gathered from this tract (Productus, Orthis, Spirifer, &c.) seem, how- 
ever, to indicate an ascending order into beds of Devonian and Carboniferous 
age ||, particularly in the wide spread of calcareous matter along the Elk and 
Slave Rivers, and upon the banks of thepMackenzie. Where the last-mentioned 
river skirts the Rocky Mountains, the limestones, more disturbed than in the 
Winnipeg basin, occupy, says Richardson, inclined and elevated ridges, the chief 
of which he considers to be Silurian ; these ridges, on the Great Bear Lake and 
the Coppermine River, abut against granite. In a letter to myself he added, a I 
believe the strata of sandstone and limestone on the north coast of America to 
be wholly Silurian, though fossils are scarce. Towards the mouth of the Cop- 
permine River there are, besides, magnificent ranges of trap with ores of lead and 
copper, including much malachite." 
To whatever extent it may be found possible to separate the Silurian rocks 
which range along the Rocky Mountains into a Lower and an Upper group, it 
would at least appear, from the specimens which have been collected by our 
naval explorers employed in the Arctic Expeditions, that the great mass of the 
most northern rocks belongs to the Upper Silurian group. This is certainly 
the case, if we judge from the collections made during the voyages of Parry, 
Franklin, Ross, Back, Austin, and Ommanney, and the private expeditions 
of Lady Franklin, particularly those of Penny and Inglefield, and the expedi- 
tion under Sir E. Belcher. The fossils brought home by these commanders 
and the officers and gentlemen accompanying them have been examined and 
described 5[ by Mr. Salter ; and from his scrutiny it results that the Crustacea 
and Mollusca are very similar to, and some of them identical with, those of 
Wenlock, Dudley, and Gothland. Among these occur : — Encrinurus laevis, Ange- 
lin ; Leperditia Balthica, His. j Pentamerus conchidium, Dalm. ; Chonetes lata ? 
* Travels in North America, 1st series, ed. 1, dom found more than half an inch in diameter ; 
vol. ii. p. 124. but these older representatives of the order were 
t The geography and geological structure of the not less than six or seven inches, and of a propor- 
great region of Eupert's Land, watered by the Eed, tionate thickness ! Mr. Billings, however, refers 
Assiniboine, and Saskatchewan Eivers, have been Eeceptaculites to the Sponges, 
ably described and mapped by Henry Youle Hind || A few specimens of the fossils of these rocks 
since the publication of my last edition. See the are in the British Museum; theyjare Upper Si- 
account of his Expedition, published by Longman lurian, Devonian, and Carboniferous. Unluckily, 
& Co. in 1860. numerous fossils brought home by Sir John 
I Bigsby and Stokes, Trans. Geol. Soc. 2nd ser. Eichardson in 1826 have been mislaid, 
vol. i. Similar Orthoceratites were found by Sir % Appendix to Sutherland's Journal of Capt. 
W. Logan further to the east, in rocks of Upper Penny's Voyage, 1850-51, (London, 1852) vol. ii. 
Silurian age. with plates. See also Quart. Journ. Gcol. Soc. 
$ Eeferred by Mr. Salter to the Foraminifera, vol. ix. p. 312, 1853. 
as a gigantic form allied to Orbitolites,which is Bel- 
