September 19, 1901] 



NATURE 



515 



further gave a table showing the vertical range of the known 

 fossils of the Caithness series from data partly supplied by the 

 late Mr. C. Peach. 



During the last quarter of a century Dr. Traquair has made a 

 special study of the ichthyology of the Old Red Sandstone and 

 Carboniferous strata of Scotland, which has enabled him to 

 throw much light on the distribution of fossil fishes in these 

 rocks and on their value for the purpose of correlation. His 

 researches show that the fish fauna of the formation south of the 

 Grampians resembles that of the Lower Old Red Sandstone of 

 the West of England and adjoining part of Wales in the abun- 

 dance of specimens of Cephalaspis, the common species in For- 

 farshire (C Lyelli, .Ag.) being also indistinguishable from that 

 in the Herefordshire beds. Pteyaspis occurs in both regions, 

 though of different species. Of Acanthodians Parexiis recur- 

 vtis, Ag. , occurs in both, together with Climatiiis (C. oriiatns, 

 Ag. ). The abundance of Cephalaspis (C CampbelUonensis, 

 Whit., C. fexi, Traq. ) and of Cliniatius spines is characteristic 

 of the Lower Devonian rocks of Canada. 



The Old Red Sandstone of Lome has recently yielded organic 

 remains, akin to those found in Forfarshire, south of the 

 Grampians, viz., Cephalaspis Lortieiisis^TxAi^.^ two species of 

 myriapods {Catiipaaris Forfareiisis&nA a $,\>tc\esoi Archidesiitiis 

 ( " Summary of Progress, Geological Survey, 1897," p. S3). 



In the deposits of Lake Orcadie, north of the Grampians, 

 quite a different fish fauna from that of Forfarshire appears. Dr. 

 Traquair has noted that there are no species common to the two 

 areas, and only two genera, viz., Mesacanlhiis and Cephalaspis. 

 The latter genus is, however, represented in Caithness only by 

 a single specimen of a species (C. inagnifica, Traq.) different 

 from any found elsewhere. It might here be observed that 

 Cephalaspis is represented also in the Upper Devonian rocks of 

 Canada by a single specimen of a peculiar species (C laticeps^ 

 Traq.), and hence Dr. Traquair has shown that, though Cephal- 

 aspis is most abundant in the Lower Devonian, it extends also 

 into the upper division of that system. It further appears 

 that Osteoiepidae (Osteolepis, Diploplertis), Rhizodontidae 

 ( Tristichopteriis ^ Gyroptychitts), Holoptychiidae [Glytolepis)^ 

 Asterolepidae (Fterichthys, Microhrachius), Cteiiodontidae [Dip- 

 tents) are abundant in the Orcadian fauna, none of which has 

 occurred in the Lower Old Red Sandstone of Forfarshire, the 

 West of England, or in the Lower Devonian rocks of Canada. 

 Dr. Traquair recognised, however, the identity of the fishes from 

 the well-known fish band in the basin of the Moray Firth with 

 those brought from the west part of Orkney, though these forms 

 did not quite agree with the fossils from the Thurso district. He 

 subsequently found that the fish fauna from the Orcadian beds 

 in the Moray Firth basin is represented in Caithness by that of 

 Achanarras ; and, further, that two other faunas occur in the 

 Caithness area — that of Thurso and that of John o' Groats as 

 given below : — 



/ Tristichopterus alains, Egert. 



\ Microhrachius Dicki, Traq. 



\ Coccostens minor, H. Miller. 



-! Thursius pholidotiis, Traq. 



(^ Osteolepis microlepidotu^. Pander. 



( Fterichthys, 3 species. 



•j Cheirolepis Trailli, Ag. 



( Osteolepis macrolepidotus, Ag. 



In 1898 appeared an important paper by Dr. Flett on " The 

 Old Red Sandstone of the Orkneys" {Trans. Roy. Soc. Edin., 

 vol. xxxix. p. 383), in which he described the results of his 

 detailed examination of the islands. He proved the existence 

 there of three fish faunas, and their correspondence with those 

 identified in Caithness by Dr. Traquair. From the evidence in 

 the field he adopted the following order of succession and 

 correlation of the strata : — 



3. Eday Sandstones and John o' Groats beds. 



2. Rousay and Thurso beds. 



I. Stromness, Achanarras, and Cromarty beds. 



A further important result of Dr. Flett's researches in the 

 Old Red Sandstone of these northern isles was communicated 

 to the Royal Society of Edinburgh this year. He has found in 

 the Shetland beds, which had previously yielded no fossils save 

 plants, fragments, identified by Dr. Traquair as Holonema, a fish 

 new to Britain, but occurring in the Chemung group of North 

 America, the subdivision of the Upper Devonian that imme- 

 diately underlies the Catskill red sandstones, with remains of 

 Holoptychius. Dr. Traquair has also recognised in Dr. Flett's 



John o' Groats. 



Thurso 



Achanarras 



NO. 1664, VOL. 64] 



collection fragments of Asterolepis, a genus characteristic of the 

 Upper Old Red Sandstone, and which, as proved by Dr. Flett, 

 occurs in the "Thurso beds" of the Orkneys. The interest 

 attaching to this discovery is very great, for Dr. Flett contends 

 that it indicates a fourth life-zone in the Orcadian series, and, 

 further, that it tends to span the break between the Orcadian 

 division and Upper Old Red Sandstone. 



In the Upper Old Red Sandstone on the south side of the 

 Moray Firth, Dr. Traquair recognised two life-zones, and sub- 

 sequently, with the assistance of Mr. Taylor, Lhanbryde, a third, 

 in the following order. The lowest is that of the Nairn sand- 

 stones with Asterolepis maxima, Ag. ; the second, that of Alves 

 and Scaat Craig with Bothriolepis major, Ag. , Fsammosleus 

 Tavlori, Traq. ; and the highest that of Rosebrae, the fauna of 

 which, according to Dr. Traquair, has a striking resemblance to 

 the assemblage in the Dura Den Sandstones in Fife. 



Before 1S76 all the Carboniferous areas in the great midland 

 valley of Scotland had been mapped by the Geological Survey. 

 The extent and structural relations of the various coal- fields were 

 determined according to the information then available, and 

 shown in the published maps. But the rapid development of 

 certain fields in the east of .Scotland necessitated a revision of 

 them which has lately been done. The Fife coal-field has been 

 re-examined by Sir A. Geikie, Mr. Peach and Mr. Wilson, and 

 the oil-shale fields in the Lothians have been mapped by Mr. 

 Cadell. An important memoir by Sir A. Geikie on " The 

 Geology of Central and Western Fife and Kinross " has just 

 been issued by the Geological Survey, in which the structure of 

 the.se coal-fields is described. Mr. Cadell lately gave an account 

 of the geological structure of the oil-shale fields in his presidential 

 address to the Edinburgh Geological Society. 



Within the period under review detailed researches of great 

 importance on the fossil flora of British Carboniferous rocks have 

 been carried out by Mr. Kidston, to which reference ought to 

 be made. The results are of the highest value for correlating the 

 strata in different areas. ' By means of the plants he arranges 

 the Carboniferous rocks of Scotland in two great divisions : a 

 lower, comprising the Calciferous Sandstone and Carboniferous 

 Limestone series ; and an upper, including the Millstone Grit 

 and the Coal-measures, there being a marked palceontological 

 break at the ba.se of the Millstone Grit. He shows that the 

 upper and lower divisions of the system, not only in Scotland 

 but in Britain, are characterised by a different series of plants, 

 not one species passing from the lower division — save in the 

 case of StigJiiaria — into the upper. From his researches it 

 appears that, among ferns, Neuropteris is all but unknown in 

 the lower division, whereas in the upper it is very abundant. 

 The Sphenopterids are proportionately common in both divisions ; 

 but those of the lower are usually characterised by cuneate seg- 

 ments, while those of the upper have generally rounded pinnules. 

 Alethopteris, so common throughout the whole of the upper series, 

 is entirely absent from the lower. The genus Catamites, which is 

 extremely plentiful in the upper, is almost entirely absent from 

 the lower division, where its place is taken by Asterocalamiies. 

 The Cordaiteae are also rare below the Millstone Grit, though 

 very plentiful above that horizon. Sigillaria, so rare in the 

 Lower Carboniferous rocks, is extremely abundant in the upper 

 division, and particularly in the middle Coal-measures. In short, 

 Mr. Kidston concludes that the floras of the two main divisions 

 of the Carboniferous system, though belonging to the same 

 types, are absolutely distinct in species, and in the relative 

 importance of the genera. 



I3y means of the fossil plants Mr. Kidston correlates the Coal- 

 measures of Scotland underlying the red sandstones with the 

 lower division of the Coal-measures of England, and the over- 

 lying red sandstones of Fife with the middle division of the 

 English Coal-measures. 



It is remarkable that the evidence supplied by the fossil fishes 

 has led Dr. Traquair independently to a similar conclusion. He 

 holds that fossil ichthyology proves the existence of only two 

 great life-zones in the Carboniferous rocks of Central Scotland — 

 an upper and a lower — the boundary line between the two 

 being drawn at the base of the Millstone Grit. The Scottish 

 Carboniferous rocks, being mostly estuarine, give an opportunity 

 of comparing the estuarine fi.shes of both divisions. He finds 

 the Coal-measure fishes of Scotland to be the same as those in 

 the English Coal-measures, while those occurring below the 



1 " On the Various Diviiic 

 lined by llieir Fossil Flora,' 

 393). 



British Carboniferous Rocks as deter 

 , Roy. Phys. Soc. Edin., vol. .xii. p. 183 



