1887. ] Mr J. EF. Marr, On Homotazis. (a) 
graptus cyphus zone of Sweden, occurs also a Dimorphograptus, a 
Diplograptus and Climacograptus scalaris, and Dimorphograptus 
dies out here. In Scotland, Monograptus cyphus is not recorded 
from this zone, but Dimorphograptus disappears here. (ii) In 
the two succeeding zones in Scandinavia, we find, (a) Monograptus 
triangulatus, M. fimbriatus, Rastrites peregrinus, &c., and (b) Mono- 
graptus convolutus, M. lobiferus, M. communis, M. leptotheca, 
Rastrites peregrinus, and Cephalograptus folium. This is the first 
appearance of Rastrites. Each one of these forms occurs in the 
gregarius zone of Scotland, along with many other species, and 
here again we mark the first appearance of Rastrites. (iv) The — 
zone of Cephalograptus cometa in Sweden contains also Mono- 
graptus spinigerus, M. intermedius, M. Clingani, M. lobiferus, M. 
argutus, Diplograptus Hughesu, Cephalograptus cometa. Each of 
them, save M. intermedius, is recorded from the two zones in 
Scotland which correspond with this Swedish zone. (v) The zone 
of Monograptus turriculatus in Sweden contains also Monograptus 
crispus, but Rastrites maximus has not been detected in it. Mono- 
graptus turriculatus however occurs in this zone in Scotland. 
The correspondence is very complete considering that our 
knowledge of these beds has only been obtained comparatively 
recently, and Prof. Lapworth informs me that the Birkhill shales 
might be further subdivided, for he paid attention to the litho- 
logical character of the beds as well as their fossil contents when 
working out the S. Scotch succession, and did not therefore trouble 
himself with making more minute subdivisions. As it 1s, a detailed 
examination of the corresponding beds in the Lake District has 
enabled me to make a very close comparison both with the Birk- 
hill shales of Scotland, and the Rastrites beds of Sweden, which I 
hope shortly to give an account of elsewhere. 
Other important facts may be gathered from an examination 
of the lithological characters of the graptolitic deposits. 1 will 
consider the case of the rocks containing the Birkhill, Gala, and 
Riccarton faunas of Prof. Lapworth. The beds containing the 
fossils are usually dark shales, but they present considerable varia- 
tions. The Birkhill beds of the Lake district consist mainly of 
black or very dark shales, the Gala beds of the same area mainly 
of pale green bands, and the Riccarton beds of grey flaggy 
rocks. . 
It might be supposed that the variations in the characters 
~ of the faunas was actually produced by variations in the nature of 
the sediment, but to prove that this is not the case, we find in 
Bohemia a succession of black shales, closely similar in general 
appearance, and nevertheless the succession of Birkhill, Gala, and 
Riccarton faunas is found exactly as in Britain. Other cases might 
be given, but one is sufficient for illustration. 
