COASTS VISITED BY THE ARCTIC EXPEDITION. 605 



to the Arenig or lowest Llandeilo series at Quebec. M. Logani, 

 Salter, occurs also in the calcareous schists of the same series at 

 Aldeans, Ayrshire, with M. magna ; and the small M. macrompliala 

 ranges into the Caradoc rocks at Craig Head near Girvan. It is in- 

 teresting to find M. magna, which is abundant in the United States, 

 occurring in the Aldeans Limestone rocks of the same age in Scot- 

 land. We do not know this genus in England or Wales ; yet no 

 less than twenty-two species occur in North America, and ten in 

 Forth Britain and Europe. The Aldeans Limestone and Arenig 

 rocks of Durness in North Scotland contain five species, through 

 three of which we are allied to North America and Canada, viz. M. 

 magna, Lesueur, M. Logani, Salter, and M. matutina, Hall. 



Maclueea magna, Lesueur. 



Maclurea magna, Lesueur, Journ. Acad. Nat. Sci. Philad. vol. i. 

 p. 312, t. 13. f. 1-3 ; Hall, Pal. N. Y. vol. i. p. 26, t. 5, 6 ; M'Coy, 

 Brit. Pal. Eoss. p. 300, t. 1-4. f. 13. 



Several specimens of this large species occur in the collection made 

 by Captain Eeilden at Cape Louis Napoleon, Cape Hilgard, Cape 

 Erazer, and Yictoria Head. Those brought home quite equal in size 

 Hall's figures in the ' Pal. New York/ vol. i. t. 5. f. 8, which occur 

 in the Chazy Limestone or " Canadian" division of the Lower Silu- 

 rian of North America (United States). This shell ranges from the 

 N.E. of York State to Kentucky and Tennessee, and N.W. to Lake 

 Superior (lat. 48°). Now we have it from lat. 80°, or 32° further 

 north. Doubtless wherever this division of the Lower Silurian 

 rocks appears, from New York to Cape Louis Napoleon, this charac- 

 teristic shell will be found. 



Mr. Salter was inclined to consider M. magna and M. Logani to 

 be the same species. M. magna was first found in Britain at 

 Knockdolian Quarry and at Aldeans (Ayrshire); its great interest 

 then as now, in this country, as in America, consists in its 

 limited geological range, being, in America, confined to the Chazy 

 Limestone (our Arenig group). We have no means of knowing its 

 geographical range here, as the Scotch rocks containing M. magna 

 strike out to sea under the Atlantic in Ayrshire. The Inch-na- 

 Danff and Durness Limestones near Cape Wrath, containing the 

 same genus, are a mere remnant of a once widely extended group 

 of rocks, and undoubtedly the same as the Quebec group, so rich 

 in Graptolites. 



Mr. Billings names and describes (but does not figure) a species 

 he terms M, ponder osa, closely allied to M. magna from the Levis 

 formation above the Chazy ; but it evidently is not the same shell. 

 We possess M. magna from the Aldeans Limestone of Scotland, and 

 M. Peachii from the Durness beds — rocks probably of Arenig age, or 

 ranging from that to Caradoc. This wide geographical range of M. 

 magna is important, and tends to show the relation of the Scotch 

 Silurian fauna to that of North America, just as the Carboniferous 

 series of Newfoundland may also be correlated with those of 

 Scotland. 



