Miscellanies. 403 
In his introduction, Mr. Lea justly remarks on the difficulty ex- 
perienced in attempting any correct and unobjectionable division of 
a family, in which the distinctive characters of species are so blended 
and run into each other, as scarcely to be separated by the most mi- 
nute care. In doing this he has certainly succeeded better than his 
predecessors, and the number of new species brought forward is 
quite remarkable. He divides the family into two genera, Marga- 
rita and Iridina, and the first into the sub-genera Unio, Margari- 
tana, Dipsas, Anodonta and Pleiodon. <A writer in the Zoological 
and Botanical Journal some time since, called in question several 
species of the genus Unio which Mr. Lea had described as his own, 
attributing them to other zoologists; these species, we observe, Mr. 
Lea still sees proper to retain, for which he doubtless has satisfactory 
reasons.—B. S., Jr. 
9. Temperature of Lake Ontario.—This lake is so large and 
deep that it never freezes in winter to any great extent. The ice 
formed along the shores in still weather is dashed to pieces, and in part 
thrown upon the banks by the first wind that raises its waves. ‘The 
ice is formed too in much greater quantity late in winter, when the 
water has had time to cool. In the severe winter of 1835-6, the 
steam boat Traveler ran through the winter from Niagara to To- 
ronto, in Canada, a distance of about thirty six miles. In March, 
of that winter, the ice once covered the water for the whole dis- 
tance and was broken through, as it was not thick, by the boat. 
The wind soon dashed the ice in pieces. ‘The ice then extended 
several miles from the westward of the lake. But so much ice is a 
rare occurrence on this lake, and takes place only in a severe win- 
ter, and late too in the season, when the waters have been unruffled 
by winds for some days, or, as the engineer of the boat remarked, 
during a long calm. 
The surface of Lake Ontario is about two hundred and forty feet 
above tide water. It is said to have been sounded to the depth of three 
hundred feet, which would place its bottom below the level of the 
sea. It is doubtful whether the statements on the depth of the great 
lakes can be relied upon. It is quite certain that some are given far 
too large. Lake Erie freezes to a great extent, if not entirely over 
its surface; but Lake Ontario is so deep that even with the dis- 
charge of the cooled water of Lake Erie into it, the waters are rarely 
lowered to the point of congelation. 
