SILUEIAN. 263 



E. O. Ulrich, having a length of IJ inches. Fragmentary specimens indicate the presence of 

 one or more other species of large ostracods, which together with a new species of Ceratiacaris 

 are associated with the large Isochilina. Other forms occurring in this portion of the section 

 are Zaphrentis ? sp., represented by a single specimen, MeristeTla tumida Dalm. ?, and Megalomus 

 sp. undt. The Megalomus is a large and very thick shelled bivalve comparable in this respect 

 with Megalomus canadensis of the Guelph and identical with a species occurring in the lime- 

 stone at Glacier Bay. 



While none of the forms occurring in the two lowest divisions of this section have been 

 identified with known species, the dominance of the large ostracods and the massive-sheUed 

 Megalomus and thick-shelled Murchisonias point to a late Silurian age of the fauna. The 

 horizon represented is apparently about that of the Guelph. 



The Silurian fauna of Freshwater Bay is found also at Glacier Bay, to the northwest. 

 A small collection in the Nation'al Museum made by Cushman and a much larger collection by 

 Mr. F. E. Wright show the faunas of the two localities to bear the closest resemblance. 



The horizon represented by the fauna at Freshwater ind Glacier bays is not known as yet 

 elsewhere in Alaska. The Kuiu Island Silurian fauna differs very materially in its facies from 

 other known Silurian faunas of Alaska, but the same horizon appears to be represented by the 

 Silurian found by the writer on the Porcupine River, in northeastern Alaska, during the last 

 summer. 



N-O 10. riNLAY AND OMENICA RIVEBS. 



Beneath the " Devono-Carboniferous " Banff limestone, in thie Peace River pass, 

 British Columbia, McConnell ^^^^ observed beds containing Halysites, Vi^hich may- 

 represent the Siloirian. They apparently correspond with the strata holding a 

 similar stratigraphic position and also containing Halysites, which occur east of 

 Columbia River on the main line of the Canadian Pacific Railway and immediately 

 overlie graptolite-bearing slates of Black River to Trenton age (Normans Kill fauna) . 

 (Seep. 191.) 



N-O 15-17. SOUTHWEST COAST OF HUDSON BAY. 



The mapping of Silurian rocks on the southwest coast of Hudson Bay rests 

 upon collections of fossils from a few isolated localities, which do not suffice to 

 delimit the formation in relation to the Ordovician rocks of the same district. The 

 most noteworthy of these occurrences is at Port Churchill, where fragments of a 

 white limestone yielded fossils related to the Silurian of the Saskatchewan and of 

 Anticosti.*^^ Farther south the limestones have been observed and fossils collected, 

 especially on Ekwan and Attawapiskat rivers. DowUng '^^^^ states: 



The valleys of all the streams entering the western side of James Bay are cut down through 

 the drift deposits to a flat-lying limestone, which forms a wide belt around the west shore of the 

 bay and along the southern shore of Hudson Bay. On the Albany River the upper part of the 

 series is proved to be of Devonian age, and beneath, at a greater distance from sea, Silurian 

 limestones are exposed. These beds probably overlap any older ones that may be beneath 

 and rest directly on the Archean. 



Descriptions and lists of fossils may be consulted.^^''®^* 



P 6-7. SOUTHERN ALASKA, COOK INLET TO YAKUTAT BAY. 



Metamorphic rocks of sedimentary origin constitute in southern Alaska a great 

 and extensively exposed series, the Valdez group, which is probably chiefly Paleozoic 

 and includes Silurian, but no definite section can be thus correlated. (See note on 

 metamorphic Paleozoic in Alaska, Chapter VII, p. 353.) 



