330 



LIFE OF THE PLEISTOCENE 



Elliptio gibbosus 

 Anodonta grandis 

 Ptyckobranchus pkaseolus 

 Eurynia recta 

 Lampsilis luleola 



" ventricosa{ = occidens) 

 Sphaerium sulcatum ( = simile) 

 rhomboideum 

 striatinum 

 solidulum 

 Pisidium adamsi 



compressum 

 noveboracense 



Amnicola limosa porala 



emarginata ( = obtusa) 

 " cincinnatiensis ( = say ana) 

 Vafoata tricarinata 

 " sincera m 

 Physa ancillaria 



" heterostropha 

 Planorbis bicarinatus ( = antrosus) 



parvus 

 Galba elodes 



" obrnssa ( — desidiosa) 

 Succinea avara 

 Bifidaria armifera ( = armata) 



Several cyprids and beetles (mostly wings) have also been obtained from 

 these beds. The mammoth or mastodon, the bison and a fish comprise the 

 vertebrate fauna. 



A study of the biota of the Don beds suggests (as previously stated by 

 Coleman and Penhallow) that during the Sangamon interval a warm climate 

 prevailed in this region, as warm or warmer than the present, perhaps like that 

 of southern Ohio or Pennsylvania. Such plants as the paw-paw {Asiminia 

 triloba), the osage orange (Madura aurantiaca), as well as species of maple, 

 ash, oak, hickory, elm and basswood, indicate a genial climate. (See Penhal- 

 low, Trans. Roy. Soc. Can., X, page 67, 1904). The unionid molluscan fauna 

 also indicates the same thing. Three species, solida, clava, and pyramidata 

 do not now live in the St. Lawrence drainage, being confined to the Ohio and 

 Mississippi valleys, farther south. Four species, phaseolus, coccineum, pustu- 

 losus, and undata still live in Lake Erie, but not in Lake Ontario. The other 

 species are now common in Lake Ontario and tributary streams. Of the 

 gastropods, Plenrocera elevatum lewisii and Goniobasis depygis do not now live 

 in the Ontario basin. The molluscan fauna is strongly indicative of the 

 Mississippi Valley region, all of the species enumerated being found at the 

 present time within its borders. The postglacial origin of the fiuviatile biota, 

 therefore, must have been in this region, where they had been crowded by the 

 Illinoian ice invasion. From here, via an outlet at Chicago or perhaps one at 

 the western end of Lake Erie (like the Fort Wayne outlet) the aquatic life 

 returned and repeopled the devastated territory. 



Immediately above the Don beds is a deposit of stratified, peaty clay, 92 

 feet in thickness, the thin sheets of peaty material, mixed with mica scales, 

 occurring every inch or two. These peaty layers, which may well represent 

 annual floods, when a Laurentian river from Georgian Bay built up a delta of 

 clay and sand in Scarboro Bay extending to the north, and communicating with 



187 Simpson (Proc. U. S. Nat. Mus., XVI, p. 593) says of this species "remarkably de- 

 pressed''; it probably should be referred to Vahata bicarinala perdepressa. Pleurocera palli- 

 dum? is mentioned by Simpson, but does not appear in Coleman's lists. 



