1897.] Recent Literature. 45 
The “ Ursa” flora of Bear Island, with Calymmatotheca, Pseudobornia, 
Lepidodendron cf. pedroanum, and Bothrodendron (B. kiltorkense and 
others), has, with the exception of the comprehensive Stigmaria ficoides, 
nothing definite in common with the Lower Carboniferous flora, and 
appears to be nearest related to the Kiltarkan flora of upper Devonian 
age, or perhaps it represents the transition from the Devonian to the 
Carboniferous. 
Finally, Dr. Nathorst discovers no difference in the character of the 
vegetation in the Devonian or Lower Carboniferous of the Arctic zone 
and that of the contemporaneous deposits in other parts of Europe, 
both the ferns and the Lycopods being of full size and apparently 
grown under conditions equally favorable, so that, so far as yet known, 
fossil plants offer no evidence of a difference in climate at those periods, 
between the Arctic and the lower latitudes of Europe. We may add 
that the same climatic conditions appear to have existed contemporan- 
eously in the Appalachian region of the United States—Davip WHITE. 
A Biological Examination of Lake Michigan in the Tra- 
verse Bay Region.—The Sixth Bulletin of the Michigan Fish 
Commission bears this title and in some one hundred pages records the 
work done by Dr. H. B. Ward and an efficient corps of assistants. 
Besides Dr. Ward’s report, there are to be found within the covers 
of the bulletin the reports of five others, either assistants or those to 
whom specimens were sent. Aquatic plants are treated by H. D. 
Thompson, the Protozoa by Dr. C. A. Kofoid, the Rotifera by H. S. 
Jennings, the Turbellaria by Dr. W. McM. Woodworth and the Mol- 
lusca by Bryant Walker. 
The objects of the work were a study of the life of the lake in all its 
manifold relations and especially of those factors which bear upon the 
welfare of food fishes in general and of the young white fish in par- 
ticular. 
The more important conclusions that Dr. Ward arrives at are: 
That 63 per cent of the food of the common white fish, Coregonus 
celupeiformis consists of Crustacea. Twenty per cent of this is formed 
by Mysis relicta Loven, and 43 per cent by Pontoporeia hoyi Smith. 
After the crustacea come small mollusks at the rate of 26 per cent, 
made up mostly of several species of Pisidium. 
That the ultimate source of the food supply is found in the plankton 
of which he estimates that there is for Lake Michigan almost 9,300,000 
cubic meters, representing a weight of from 102,300 to 118,600 metric 
tons, or 12 to 16 pounds to each acre of surface. With Hensen he 
