Reviezv of Rece?it Geological Literature. 383 
netite, apatite and perofskite, with secondary calcite. The investi- 
gation is largely based upon the methods established by Merrill. Both 
the fresh rock and its highly weathered faces were analyzed, the chief 
points of interest being, as usual, the increase of ferric oxide and water 
and diminution of ferrous oxide, alkaline earths and silica in the 
weathered material. From the analyses the loss for the whole rock, 
and the percentages of each constituent retained and lost are calcu- 
lated. The titanic oxide is shown to be one of the most resistant 
constituents of the rock, its behavior being almost identical Avith that 
of alumina, so that the two are taken together as the basis for com- 
parison. The iron oxides have proved almost equally insoluble, the 
apparent net increase being due, of course, to per oxidation of FeO. 
The large proportion of magnesia and lime in the weathered rock in- 
dicate that the process is far from complete; and in harmony with this 
view 93.60 per cent, of the weather reck was found to be soluble in 
hydrochloric acid and sodium hydrate solution. The contrast between 
the surface weathering and deep-seated alteration of rocks, the rate 
of decomposition of biotite, and the time of wathering are also dis- 
cussed. Biotite appears to weather rapidly in acid rocks and slowly 
in basic rocks simply because, while it is chemically one of the weak- 
est constituents of the former, it is one of the most resistant constitu- 
ents of the latter, the difference being relative only. w. o. c. 
Om AcEROCAREZONEN ett bidra£[ till Kdrmedomen 0171 Skanes Ole- 
nidetiskiffrar, af JOH. Chr. Moberg och Hjelmar Moller [Geol. 
foren i Stockholm forhandl., Bd. 20, Hf. 5, 1898.] 
This valuable contribution of Moberg and Moller to a knowledge 
of the upper Olenus schist of Scania largely extends our knowledge of 
the range of the genus Acerocare. Hitherto we have thought it was con- 
fined to the layer immediately beneath the Dictyonema shale, but this 
essay shows that it had a wider range, viz: through the whole thickness 
of the Peltura or upper Olenus schist, and that the type of the genus A. 
ecorne Angelin, in place of coming at the top of this fauna, is really at 
the base. The genus is carried up through the Peltura beds by several 
species, one described by Linnarsson, and several new, by these authors. 
They also describe a new species of Parabolina, and give, fuller illustra- 
tions of P. heres Brogger, than had been given by the author of the spe- 
cies. The figures of this species differ considerably from Brogger's, no- 
tably in the heavy wrinkling of the test, and the deep glabellar furrows. 
One valuable feature of this work is that young head shields are figured, 
thus giving a much better conception of the genetic relationship of the 
species, than the figures of adult shields alone would give. 
The authors relegate 0/eniis acanthurus Ang. which Brogger had 
placed in Protopeltura (Brog) to Parabolina, Salter. Acerocare is re- 
garded as a genus closely related to Peltura, differing from it in the 
spineless pygidium etc. 
An excellent feature of this article is that restorations of the complete 
form of most of the species described arc given, and the hypostome also 
in most cases. Five excellent plates accompanv the article, and leave 
