264 
SILURIA. 
[Chap. XI. 
Fossils (72). 
Cranial Bone of Diplopterus. 
the subjoined small woodcut, which exhibits the frontal portion of the 
cranium of Diplopterus borealis *. The jet-like lustre of some of the 
Caithness and Orkney Ichthyolites and the 
blackish-purple and dark-blue colours of 
others, make them very conspicuous objects 
in the grey flagstone. 
The central or Caithness flags near Wick 
have also afforded, to the researches of Mr. 
C. Peach and others, forms which, resem- 
bling shells, have been spoken of as such ; 
but they are now shown by Professor 
Eupert Jones to be the bivalve carapaces 
of the Crustacean genus Estheriaf. E. 
membranacea, Pacht, abounds in the flag- 
stones of Caithness, and is plentiful also 
in the Devonian sandstones of Livonia. 
The bituminous schists of the North of Scotland thinning out in their 
range southwards, the next member of the series in the central parts of 
Scotland is specially characterized by other Ichthyolites. It is, however, 
to be observed that the central group of Ichthyolites, which specially cha- 
racterizes the bituminous flags of Caithness and the Orkney Islands, is found 
at various places as we proceed southwards along the east coast of Scotland. 
Thus, at Edderton, in Eoss-shire, the Eev. J. M. Joass has discovered in 
red sandstone a considerable number of the genera. Traces of the same 
Fishes have been found in the Black Isle ; and Hugh Miller has described 
them from near Cromarty. They are seen at intervals in Inverness-shire, 
Nairnshire, and Morayshire i, and reappear on the banks of the Spey near 
* From a specimen found by Dr. Hamilton of Council, until Agassiz, the great authority on 
Frontal portion of the cranium 
of Diplopterus borealis. From 
the dark grey flagstones of Strom- 
ness, Orkney. 
Stromness. For the entire cranium see Hugh 
Miller's Footprints of the Creator, p. 58. He 
particularly refers to the small central plate in 
the frontal bone as common to most of the Ga- 
noids of the Old Bed. 
t Monograph of the Fossil Estherise, Palseon- 
tograph. Soc. 1862. 
T Already in 1828 Professor Sedgwick and my- 
self united into one geological group the lower 
red conglomerate and sandstone, intervening corn- 
stones, and the yellow fish-bearing sandstones of 
Elgin. We further showed that the fish-bearing 
zone of Caithness was traceable to the south-east 
of Inverness as a thin course of shale, though we 
there detected no Fishes in it. (Trans. Geol. Soc, 
2nd ser., vol. iii. pp. 147, 150 et seq.) 
The remains of Fishes were not discovered until 
nine or ten years afterwards, — first, I believe, by 
the zeal of the late Dr. J. Malcolmson. Lady 
Gordon Cumming, so well known to the readers 
of the works of Agassiz and Hugh Miller, followed 
up these researches. Dr. Malcolmson, when on 
leave of absence from the East Indies, detected 
several of the Caithness Fishes at Clune and Le- 
then Bar in Nairnshire ; and, having followed up 
his discoveries into Morayshire, he presented to the 
Geological Society a detailed memoir descriptive 
of these tracts in 1839. This paper was to be printed 
in the Transactions of that Society; but, as the 
author spoke doubtinglv respecting the genera and 
species of his fossil Fishes, the ord 
lication of the memoir was d< 
er for the pub- 
f erred by the 
Ichthyolites, should have determined the specific 
characters of those fossils. In the meantime an 
abstract, giving the main features of the la- 
bours of Malcolmson, was published (Proceed- 
ings Geol. Soc. Lond. vol. iii. p. 341) ; and shortly 
afterwards that accomplished man, having re- 
turned to India, fell a victim to his zeal in pur- 
suing geological researches in the jungles of the 
Bombay Presidency. Subsequently, in 1859, the 
substance of this memoir, with its illustrative sec- 
tions, was published in the Edinburgh New Phil. 
Journal (January, 1859), by the Eev. G. Gordon, 
and in the Quart. Journ. Geol. Soc. London, 
vol. xv. p. 336. Dr. Gordon has well illustrated 
all the fish-bearing strata around Elgin which be- 
long to the Old Bed Sandstone, as well as those 
overlying sandstones which I now refer to the age 
of the Trias, as will be presently explained. 
In mentioning those persons who, in addition 
to Hugh Miller, Malcolmson, and others, have 
done such good geological service on the north- 
east coast of Scotland, I am bound to go as far 
back even as my own earliest researches of 1826, 
and to state that my friend Mr. George Anderson, 
of Inverness, has thrown much light upon parts of 
his native country, and has been of great use to 
many an explorer besides myself. Mr. Anderson 
is well known to all tourists as the author of the 
' Guide to the Highlands,' in the third edition of 
which (pp. 344 to 349 &c.) the reader will find an 
able summary, by the late Mr. Alex. Bobinson, of 
the Geology of the Moray Firth. 
