of Edinburgh^ Session 1877 - 78 . 
599 
Thickness 
in feet. 
9. John o’ Groats red sandstones, flagstones, and 
impure limestones and shales, . . . 2000 
8. Huna flagstones, shales, and limestones, . . 1000 
7. Gill’s Bay red sandstones, .... 400 
6. Thurso or northern group of flagstones, shales, 
and limestones, ...... 5000 
5. Wick or eastern group of flagstones, shales, and 
limestones passing down into red shales and 
sandstones, ....... 5000 
4. Dull red sandstones, red shales, and fine con- 
glomerates, . . . . . . .2000 
3. Brecciated conglomerates, .... 300 
3. Badbea red sandstones and shales or clays, . 450 
1. Coarse basement conglomerates, ... 50 
- 
16,200 ft. 
From the four lowest sub-divisions no fossils have yet been 
obtained. The flagstones have yielded to Mr C. W. Peach and 
other observers many land plants (some of which resemble forms 
described by Dawson from the Gaspe sandstones) as well &$Estheria 
membranacea , Pterygotus, sp., and many ichtliyolites. Availing 
himself of the list of localities furnished to him by Mr Peach (to 
whom he cordially acknowledges his obligations), with the species of 
fish found at each, the author has constructed a table of the vertical 
distribution of the fossil fishes in Caithness. Some of the species 
range through almost the entire succession of beds. Some, how- 
ever, are either peculiar to or very characteristic of one sub-division. 
Thus Osteolepis arencdus and Dipterus Valenciennesi are not noted 
except from the group No. 5. In the Thurso and the higher 
flagstones (Nos. 6, 8, and 9), Acanthodes, Parexus, Clieir acanthus, 
Diplacanthus, Ptericlithys, and Tristicliopterus — genera absent from 
the Wick beds — are found in greater or less abundance. These 
strata are further marked by peculiar species of genera which occur 
among the older flagstones, as Coccosteus pusillus and Ostaolepis 
microlepidotus. 
The Orkney Islands are assigned to the higher sub-divisions of 
