Rev ieio of Recent Geological Literature. 55 
forms have been too minute to show satisfactorily the details of struc- 
ture, both the developmental stages and full grown shell have been 
enlarged to a convenient size. Thus the incipient stages and mature 
specific forms are presented together." 
Among its facts of interest brought out by the investigation here re- 
ferred to is that the initial stages of very distinct species, and even of 
very distinct groups, are so much alike, that it is often impossible to 
say whether a given embryo is the young of Spirifer, Athyris ,Rhynchon- 
ella, Anastrophia, Meristina or Nucleospira. The conclusions of the 
authors, however, do not admit of any condensed statement and persons 
interested in the subject are referred to the original paper. 
Report on the geology of the Rainy lake region. By Andrkw C. Lawsonv 
Ph. D. (Part F of the Annual Report of the Geological and Natural 
History Survey of Canada for 1887.) pp. 190, with two maps, 7 sections, 
7 plates from photographs, and 15 cuts in the text illustrating the 
microscopic features of thin sections of rocks. Montreal, 1888. 
In this approximately plain or moderately hilly Archaean region, so 
thinly covered by the glacial drift that often the bed-rocks are exposed 
to view almost continuously along distances of many miles, exception- 
ally favorable opportunity is afforded for their study. But the unin- 
habited condition of the country (forest and swamp, without roads) 
permits extensive travel only by canoes and by portages across the 
narrow divides between lakes at the head of the stream-courses. 
The Archaean group there is found to be divisible into two systems, 
the lower being the granitoid gneisses, to which the name Laurentian 
is restricted by Dr. Lawson, and the upper being chiefly schists, which 
are again divided into two series. The older of these, consisting of 
mica schists and granitic gneisses, with a measured maximum thick- 
ness of four or five miles, is named by Lawson the Coutchiching series, 
well developed about Rainy lake ; and the newer, including metamor- 
phosed volcanic rocks, with schists, grey wackes, quartzytes and slates, 
he has called the Keewatin series in a former report on the region 
about the Lake of the Woods. The present report gives very abundant 
and interesting observations of these formations, and ably discusses 
their origin and age, the history of their metamorphism, and their 
present structure and relationship. 
The author's studies lead him to believe that after the deposition of 
the stratified formations which constitute the upper part of the 
Archaean in these districts, the whole group comprising a vast thick- 
ness of sedimentary and volcanic rocks and perhaps below including a 
part of the first formed crust of the globe, was sul)jected to metamor- 
phism from the heat of the earth's interior, whereby the basal Lauren- 
tian rocks were so fused that portions of them were extravasated 
through the overlying Coutchiching and Keewatin series. The Lauren- 
tian system can there be classified only on a petrographical basis, as 
its distinctions of stratigraphical sequence and relationships, if any 
such ever existed, have been obliterated. All the characters of those 
