Dr. H. A. Nicholson on Dredgings in Lake Ontario. 211 



of which is comparatively low. All the shells in this clay 

 are dead, but it contains numerous small Annelides of the 

 genus Scenuris, along with many larvte of a Dipterous insect 

 allied to Chironomus or Corethra^ the latter being very con- 

 spicuous from their brilliant red colour. The muddy bottom 

 seems to be wholly destitute of weeds, and does not appear to 

 encroach upon depths of less than 2 fathoms. 



Towards the edges of the bay, where the depth diminishes 

 to one and a half fathom or less, the bottom consists of sand, 

 covered over considerable areas by a dense growth of weeds 

 of different kinds. The chief varieties of bottom in this 

 shallow zone are these : — 1 . Pure siliceous sand with dead 

 shells, almost destitute of life. 2. Sandy mud with a dense 

 growth of Charas, containing numerous Gamniari, small 

 leeches, larvte of Chironomus and Ephemerids, with shells of 

 Uyiio^ Gyclas^ Paludina^ Planorhis^ Valvata, 3Ielania, Pisi- 

 dium, and Physa. 3. Sandy mud, sometimes Avith peaty 

 layers, supporting a dense vegetation of ^«acAar«5 canadensis 

 and Charas. The life in these portions of the bay consisted 

 of much the same animals as in the preceding, except that the 

 Gammari were absent, unless in the occasional patches of 

 Charas brought up by the dredge. In some places, in from 

 one to one and a half fathom of water, the sand was crowded 

 with UnioneSj the dredge coming up completely packed with 

 living and dead shells. This was especially the case at several 

 points under the lee of the " island," a long, flat, insulated 

 strip of land which forms the southern boundary of the bay, 

 running parallel with the shore on which Toronto is built, at 

 a distance of about a mile and three quarters from it. 



Another series of dredgings was carried on from a point in 

 the open lake, about eight miles to the south of Toronto, on a 

 line extending to the Toronto rolling-mills, the depth varying 

 from 40 fathoms at the southern end of the line to 3 fa- 

 thoms at its northern extremity. The deep dredgings along 

 this line were only partially successful, the dredge bringing 

 up nothing but good-sized pebbles, all the finer materials 

 having been washed out before it reached the surface. In 

 about 15 fathoms the bottom was found to consist of a tena- 

 cious blue clay, distinctly laminated, and containing numerous 

 broken-up stems of plants, along with small pebbles. No 

 traces of life could be detected beyond a few minute Anne- 

 lides belonging to the genus Soinuris. Another haul in 10 

 fathoms brought up the di-edge full of sand and pebbles with 

 no traces of life ; and another in 8 fathoms showed a bottom 

 of clear sand with dead shells of Cyclas and Pisidium^ but 

 devoid of all vestiges of animal or vegetable life. 



