DEVONIAN FAUNA. 73 



wholly collected by the Geological Exploration of the Fortieth Parallel, 

 Eureka has now furnished no less than twenty-three genera and thirty-live 

 species. 



In the collections from Eureka, occur two species, lirst described by 

 Mr. F. B. Meek," Ortliis macfarleni and Bhi/ndioneUa castama, from the Mac- 

 kenzie River. Both of these important species were brought to this country 

 by the late Mr. Robert Kinnicut, and were found associated together on 

 the Lockhart River, a tributary of the Mackenzie, in latitude 67° 15' north, 

 longitude 126° west, while the OrtJm was also obtained in a very similar 

 limestone 40 miles below Fort Good Hope, on the Mackenzie. According 

 to Mr. A. K. Isbister,' who traveled extensively in Northern British Amer- 

 ica, along the base of the Rocky Mountains, and avIio published a sketch 

 map of its geology, the Devonian extends tlirough the valley of the Macken- 

 zie from its mouth southward for 15° of latitude, nearly, if not quite, to the 

 headwaters of the Saskatchewan River. It certainly is of considerable 

 interest to find these two species, which occur together in the Ai-ctic 

 regions, associated at Eureka in the upper members of the Lower Devonian 

 They are found near Woodpeckers Peak, about 3,000 feet above the base 

 of the limestone, while B. castanea was also obtained from the upper hori- 

 zon at Rescue Hill. 



Within the area covered by the Nevada limestone collections of fossils 

 were made more or less complete from nearly forty localities. For the pur- 

 pose of this volume it seems hardly desirable to publisli the lists in full, 

 and such only are made use of as may be necesesar}- to elucidate for 

 geological purposes the faunal development and also to point out clearly 

 upon what evidence the division into two groups is based. Of the 6,000 

 feet included within the epoch, 4,000 are provisionally assigned to the lower 

 and 2,000 to the upper horizon. About two-thirds of the species belong to 

 the lower and one-third to the upper, con-esponding roughly to the relative 

 thicknesses of the two hoiizons. The upper portion of the limestone, 

 howevei", represents a fauna equally varied, although not so complete, as 

 the lower. So far as they have been studied the upper and lower horizons 

 furnish quite characteristic faunas, with only seventeen species which may 



' Trans. Chi. Acad. Sci., vol. i, pt. 1, 1867-'69, p. 88. 



-Quarterly Journal, Geological Society, vol. xi, London, 1855, p. 497. 



