Page:Proceedings of the United States National Museum, Volume 76.djvu/132

4 creating some doubt as to the exact contemporaneity of these deposits laid down in two areas separated by only 6 miles. This discrepancy may, however, also be explained by a geographic arrangement whereby the one area was enabled to get more constant restocking from the common parent sea. No question, however, remains concerning the relative position of these beds in their respective sections. The Burgess shale definitely underlies the massive, usually unfossiliferous Eldon limestone, which closes the Middle Cambrian sequence at many places in the Canadian Rockies. Fossils have been reported in the Eldon from localities chiefly to the east and north of Field, and until these and the fossils of underlying formations are studied nothing further can be said concerning the age of the Burgess shale. However, with the information now in hand the statement that its position is above the middle of the Middle Cambrian seems undeniable.

At present it is not possible to say exactly what position the soft yellow shales from central Manchuria hold. From the scanty information in hand it would appear that these shales are either interbedded with or directly overlie the oolitic limestones containing Dorypyge richthofeni. In either case this bed is succeeded by a non-oolitic limestone containing the Asiatic Drepanura fauna, which apparently belongs to the Middle Cambrian and may therefor have been deposited at the same time as the Eldon, while the underlying oolitic and shaly beds, with a Dorypyge fauna, are to be correlated with the upper part of the Stephen. At any rate, considering the Manchurian section as now known, as being fairly representative of Middle Cambrian time, this yellow shale would hold a position somewhat above the middle of that division, and hence be in the same relative position as the Stephen formation. Additional data have recently been secured which we hope will throw more light on the problem and possibly clear up some of the uncertainties.

The Cranbrook locality has yielded a most interesting Lower Cambrian fauna that contains some new elements, particularly a new Mesonacid genus, but which in general agrees with what we ordinarily expect in a Lower Cambrian Mesonacid fauna. This same fauna has been collected from red and gray limestones and from sandstones in the vicinity of the Upper Columbia Lake and seems to continue northward into the Dogtooth Mountains, as the equivalent of the lower Mount Whyte fauna, with the possibility that it is also the same as the Hota fauna at Mount Robson. At Cranbrook the relatively soft Tuzoia beds, composing the Eager formation, outcrop but poorly and consequently their relative position is not