Review of Recent Geological Puhlications. 59 
The Crinoidea are sub-divided into two great groups, Epascocrinen 
and Hypascocrinen; according to whether the moutii and food grooves 
are open or closed. The division of the Crinoidea based upon this 
character has recently been shown to be untenable and has been 
abandoned. The second volume of this important work will be issued 
shortly. C. R. K. 
The Archean Geology of the region northwest of lake Superior. By 
AxDKEw C. Lawson. (In Etudes sur les schistes crislallins; published 
by the Comitc d' organization of the late London session of the Inter- 
national Congress of Geologists, London 1888.) In this paper are given 
concisely the main points reached by the author in his late studies in 
the region mentioned, for the Canadian geolojjrical survey. The rocks 
of the Archean he divides into upper and lower divisions, the lower 
being the gneisses and syenites of the Laurentian, and the upper the 
crystalline schists and the sericitic schists and graywackes. He regards 
the Laurentian as the ancient floor on which the upper Archean was 
deposited, but which has since been fused and rendered "magmatic," 
so as to penetrate fissures and overflow considerable areas of the upper 
Archean ; that primarily an older rock it is, in its present condition 
and position, a younger rock than the schists. The upper Archean he 
describes as a very distinctly stratiform assemblage of rocks, partly of 
detrital sediments and partly of volcanic ejectamenta, separable into 
Coutchiching, the crystalline schists proper, and Keewatin, or the 
sericitic schist group. The former were laid down in a period of 
extreme quiescence, but the opening of the Keewatin "appears to have 
been the beginning of a widespread volcanic activity which lasted 
throughout." There is apparent conformity between the two series, 
according to the author, but owing to the profound contrast in petro- 
graphic characters he considers that the line of demarkation between 
them represents an historical break which is of the nature of an 
unconformity. 
As to the nature of the contact between the upper Archean schists 
and the lower Archean gneiss, the author recognizes the difficulty 
which geologists will find in accepting his hypothesis that the gneiss 
is both older and younger than the schists. "There is now no trace of 
that fioor, in the condition in which it must have been when other 
rocks were laid upon it." * * * "On the contrary it presents the 
most convini'ing evidence of bearing the same relation, subject to 
certain qualifications, to the upper Archean that an eruptive rock 
bears to the strata through which it breaks." The author conceives 
that the Laurentian sediments were depressed, after the accumula- 
tion of tlie upper Archean, so as to come within the fusion plane of 
hydro-thermal agents, and that they were in this magmatic condition 
not only re-crystallized but were extruded through the upper Archean, 
which the author supposes did not experience this fusion, or if it did 
the original rock was converted to Laurentian hornblende-syenite (if 
from the Keewatin) or Laurentian biotite-granite-gneiss (if from the 
sediments of the Coutchiching). 
