Reviews—W. C. Brogger—On the Silurian of Sweden. 317 
shales, contain the genus Bryograptus in Norway. Prof. Brogger | 
supposes that these genera will be found to occupy similar positions 
in Britain also, and that they will each mark a distinct horizon, 
older than the Phyllograptus shales. 
The author remarks that the Ceratopygekalk Sa y has been pre- 
viously correlated with the Tremadoce slates, and points out that a 
few Ceratopygekalk genera occur in the Welsh beds, as Huloma, 
Niobe and Dikellocephalus. 
A careful analysis of the fossils of Hof in Bavaria is also made, 
and the comparisons are of interest to British geologists. Linnars- 
son’s identification of some of M. Barrande’s species of Conocoryphe 
with Niobe is mentioned; Asaphus Wirthi is also considered to be 
most nearly allied to Niobe ; Huloma is perhaps represented by 
Conocoryphe Geinitzi, etc. ; Conocoryphe ? problematicus may possibly 
be a Syntphysurus; Agnostus Bavaricus represents A. Sidenbladhi ; 
Cheirurus gracilis and C. discretus appear to be related to C. foveo- 
latus and Amphion primigenius; Bavarilla Hofensis is possibly a 
Neseuretus. According to this analysis, the beds of Hof, containing 
this fauna, correspond with the lowest part of the Tremadoc slates, 
and approximately with the Norwegian Ceratopygeschiefer, in Prof. 
Brogger’s opinion. 
The importance of these comparisons should not be overlooked by 
English geologists. Both Linnarsson and Brogger consider the Hof 
beds to be more nearly allied to the second fauna of M. Barrande 
than to his primordial fauna, and this has also been pointed out by 
M. Barrande himself. Professor Brogger, in his book, gives strong 
reasons for bracketing the corresponding Ceratopyge beds with the 
Asaphus-etage (which contains also the Phyllograptus Schiefer, the 
representatives of the Arenig beds), rather than with the Olenus- 
etage (representing the Lingula Flags). Notwithstanding these 
affinities, many English geologists still insist upon drawing a hard 
and fast line between the Tremadoc slates and the Arenig beds, 
whereas if any line were to be drawn about this horizon (which 
appears unnecessary), it should be at the base of the Tremadoc 
slates. 
The fourth section of the work is occupied with a discussion of the 
development of the fauna of stages 1—3.. It is full of suggestive 
matter, and is accompanied by a table of the vertical distribution of 
the fossils. A very good illustration of the danger of basing con- 
clusions upon negative evidence is given when considering M. 
Barrande’s observations about the absence of Cephalopoda from the 
primordial fauna. Professor Brégger points out that no Cystideans 
have been found among the primordial fauna in Sweden, Norway, 
and Russia; from this, he says, we might conclude that there were 
no Cystideans at this time, and yet they are found in the primordial 
beds of England and Bohemia. 
_ The fifth section is devoted to a description of the disturbances 
which have affected the strata, and the erosion of the beds. A 
number of very complex inversions are described and figured, many 
of which would be very difficult to detect, were it not for the com- 
