POSTGLACIAL BIOTA OF THE GREAT LAKES REGION 161 



cause tamarack and spruce had time to grow and thrive at Hamilton. In the 

 Don Valley, at Toronto, there are valleys of erosion in the interglacial till 

 which also attest an extensive stage of low water. Coleman further suggests 

 that the erosion in the Don Valley may have been pre- Warren. It might pos- 

 sibly represent the Lake Arkona stage. 



3. Nipissing Great Lake Stage 

 The City of Owen Sound is built upon both the Algonquin and Nipissing 

 beaches, the former at 748 and the latter at an elevation of 625, 627, and 633 

 feet. 147 Many years ago, Robert Bell 148 listed several species of mollusks 

 which were collected from the bank of the Sydenham River, 9 feet above the 

 lake. Mollusks were obtained at higher elevations also. As the datum for 

 Lake Huron is 581.5 feet A.T., the deposit from which the shells were secured 

 was at an elevation 600.5 feet. This is below the crest of the Nipissing beach 

 (625 to 653 feet) and the specimens are therefore referable to the Nipissing 

 stage. The following species are listed by Bell. 149 



Sphaerium simile Vahata sincera 



Campeloma decisum " tricarinata 



Goniobasis acuta (— haldemani) Planorbis bicarinatus ( = antrosus) 



conical" " campanulatus 



livescens " parvus 



Amnicola limosa porata Galba umbrosa ( = elodes) 



Pyramidula alternata 



About a mile south from the river, a lacustrine deposit of sand containing 

 shells was found, upwards of 30 feet above the lake (Bell, I.e., p. 51). These 

 might be referable to a period between the Algonquin and Nipissing stages. 



In the area south of the Ottawa River, west of the city of Ottawa, a num- 

 ber of marl deposits occur. These are in lakes of greater or less size and the 

 deposits vary- in thickness from 4 to 12 feet. 151 The best localities are noted 

 below: Mink Lake, near Eganville; chain of lakes in Ross Township, extending 

 southeast from Muskrat Lake; lake bottom on lots 9 and 10, Westmeath Town- 

 ship ; all in Renfrew County. These lake and pond beds represent depressions 

 in the bottom of the outlet of the Nipissing Great Lakes and the fauna con- 

 tained in these deposits may be referred to this stage, tho a portion of them 

 may have been laid down at a later period, particularly the surface layers. 

 Seven species of mollusks are recorded by Ami. 152 



Elliptio complanatus Physa heterostropha 



Anodonla fluviatilis Planorbis campanidatus 



147 Goldthwait, Mem. Can. Geol. Surv., X, p. 23. 



148 Can. Nat., VI, p. 50. 



149 It is impossible to verify these records, and they are listed substantially as originally 

 recorded by Bell in Can. Nat., VI, p. 50 and Geol. Can. 1863, p. 967. 



1511 Foot-note number 130. 



151 Ells, Rep. Geol. Surv. Can., No. 977, p. 46. 



152 Rep. Geol. Surv. Can., 1899, pp. 53, 71. 



