5i6 



NA TURE 



[September 19, 1901 



Millstone Grit in Scotland are mostly different in species, and 

 often, too, in genera, from the forms above that horizon. 



Of special interest as bearing on the former extension of this 

 system in Scotland is the discovery made by Prof. Judd {Quart. 

 Journ. Geol. Soc, vol. xxxiv. p. 6S5) in 1877 of a patch of Car- 

 boniferous sandstones and shales, with well-preserved plant 

 remains in Morven. Another small outlier of this formation has 

 recently been found in the Pass of Brander by the Geological 

 Survey (" Summary of Progress, Geological Survey," 1898, 

 p. 129). 



The reptiles from the Elgin sandstones, recently described by 

 Mr. E. T. Newton (Phil. Trans., vol. clxxxiv. 1893, P- 43') ; 

 ihid., vol. clxxxv., 1894, p. 573), add fresh interest to the study 

 of these rocks. The structural relations of these sandstones 

 have been fully treated by Prof Judd in his great paper on the 

 Secondary Rocks on the east of Scotland {Quart. Journ. Geol. 

 Soc, vol. xxix. p. 98), and again in his presidential address 

 to this Section at Aberdeen (Rep. Brit. Assoc, for 1885, p. 994), 

 who confirmed Huxley's well-known correlation of these beds 

 with the Trias. The Dicynodont skull, identified by Prof. Judd 

 and Dr. Traquair at the Aberdeen meeting of the British 

 Association in 1885, and other remains found in the reptilian 

 sandstones in Cutties Hillock (Juarry, where they rest on Upper 

 Old Red Sandstone with Holoptychius, have been described by 

 Mr. Newton. He confirmed their affinity with Dicynodonts, 

 though they were referred to the genera Gordonia and Geikia. 

 But the most remarkable specimen was the skull named by Mr. 

 Newton Elginia niirabilis. This extraordinary creature, with a 

 pair of horns projecting like those of a short-horned ox, and 

 with smaller spines and bosses, numbering thirty-nine, is related 

 to the great Parciasajirus from the Karoo beds of South Africa. 

 Two other reptiles are described by Mr. Newton from this 

 quarry, namely, a small crocodile-like animal, Erpetosuchus 

 Granti — apparently nearly allied to Stagonolepis — and Ornilho- 

 suchus IVoodwardi, which is probably a small Dinosaurian. 



Mr. Newton has raised an interesting point in connection 

 with his researches. He calls attention to the fact that the 

 reptilian remains from the Cutties Hillock Quarry differ from 

 those found at other localities in the Elgin district. For 

 example, the Lossiemouth sandstones have yielded Stagonolepis, 

 Hyperodapedon and Telerpeton ; and the Cutties Hillock sand- 

 stones, the Dicynodonts {Gordonia and Geikia), the horned 

 reptile (Elginia), the small crocodile-like Erpetosuchus, and the 

 little Dinosaurian Ornithosuchus. Does this distribution indi- 

 cate different stratigraphical horizons? is viritually the point 

 raised by Mr. Newton. In connection with this inquiry he cites 

 the evidence obtained in other countries. Thus, in the Gond- 

 wana beds of India, the series of reptiles similar to those of 

 Elgin occur at different localities and on different stratigraphical 

 horizons ; Dicynodonts and Labyrinthodonts being found in the 

 lower Panchet rocks, while Hyperodapedon and Parasuchus (allied 

 to Stagonolepis) are met with in the higher Kota-Maleri beds. 

 Again in the Karoo beds of South Africa the Dicynodonts and 

 the great Parciasaiirus — the latter being the nearest known ally 

 of the horned reptile {Elginia niirabilis) from Cutties Hillock, 

 Elgin — occur low down in that formation. Further light is 

 thrown on the question by the interesting discoveries of 

 Amalitzky in Northern Russia, where a number of reptilian re- 

 mains have been found closely allied to Pareiasaurus, Elginia 

 and Dicyttodon, in beds, which are referred to the Permian 

 formation and accompanied by plants and mollusca which 

 seemingly confirm this reference.' 



In view of these foreign discoveries Mr. Newton concludes 

 that the Elgin sandstones may probably represent more than one 

 reptilian horizon, and that we are confronted with the possibility 

 of their being of Permian age. 



The difficulty of drawing a boundary line between the Trias 

 and the Upper Old Red Sandstone of Elgin, which impressed 

 the mind of the late Dr. Gordon, has had to be faced elsewhere 

 in Scotland. In Arran, my colleague, Mr. Gunn, has shown 

 that the Trias there rests on Upper Old Red Sandstone, both 

 formations having a similar inclination. Even he, with his ripe 

 experience, has had great difficulty in drawing a boundary be- 

 tween them on the west side of the island ; but when the base 

 line of the Trias is traced eastwards to Brodick it passes trans- 

 gressively on to Carboniferous rocks. 



Of special importance is the recent discovery in Arran of the 

 fossils of the Avicula contorta zone ("Summary of Progress, 



89Q de debris de vertebras dans les 

 (Var.sovie, 1900.) 



1 Y. Amalitzky, " Sur les fouille: 

 dcpSts Penniens de la Russiedu n 



NO. 1664, VOL. 64] 



Geological Survey, 1899," p. 133) by Mr. Macconochie, of the 

 Geological Survey, to whose skill as a fossil collector Scottish 

 geology owes much. With these occur Lower Liassic fossils, in 

 sediments which are not now found in place in the i.sland. These 

 fossiliferous patches are associated with fragmental volcanic 

 materials filling a great vent, the age of which will be referred 

 to presently. This discovery has fixed the Triassic age of the 

 red sandstones and marls in the south of Arran. The detailed 

 mapping of the island by Mr. Gunn has demonstrated that 

 the Triassic sandstones rest partly on the Old Red Sandstone, 

 partly on the Carboniferous Limestone Series and partly on the 

 Coal-measures. 



In 187S appeared the third of Prof. Judd's great papers on the 

 Secondary Rocks of Scotland, wherein he unravelled the his- 

 tory of these strata as developed in the east of Scotland and in 

 the West Highlands. His admirable researches, in continuation 

 of the work done by Bryce, Tate and others embraced the 

 identification of the life-zones, their correlation with those of 

 other regions, the history of the physical conditions which pre- 

 vailed in Scotland during Mesozoic time, and the working out 

 of the structural relations of the strata (Quart. Journ. Geol. Soc, 

 vol. xxix. p. 97, vol. xxxiv. p. 660). He showed that their pre- 

 servation on the east of Scotland was due to the existence of 

 great faults, and those in the West Highlands to the copious out- 

 pouring of the Tertiary lavas. He was the first to detect the 

 occurrence of Cretaceous rocks in the West Highlands, and to 

 show the marked unconformability which separates them from 

 the Jurassic strata. His main life-zones and his main conclu- 

 sions regarding the Secondary Rocks of Scotland have so far 

 been confirmed by the detailed mapping of the Geological 

 Survey. An interesting addition to our knowledge of these rocks 

 was made by my colleague, Mr. Woodward, in the course of his 

 field work, who found the oolitic iron ore in the Middle Lias of 

 Raasay, the position of which corresponds approximately with 

 that of the Cleveland ironstone (Geo/. Mag., December 3, vol. 

 X. p. 493 (1893). 



The extensive plateau of Tertiary volcanic rocks in the Inner 

 Hebrides has been a favourite field of research ever since the 

 time of Macculloch, the great pioneer in West Highland geology. 

 During the period under review much work has been done in 

 that domain. According to Prof Judd, that region contains the 

 relics of five great extinct volcanoes and several minor cones, 

 indicating three periods of igneous activity. The first was 

 characterised by the discharge of acid lavas and ashes, the 

 molten material consolidating down below as granite ; the 

 second by the outburst of basic lavas, now forming the basaltic 

 plateau, connected with deep-seated masses that appear now as 

 gabbro and dolerite ; the third by the appearance of sporadic 

 cones, from which issued minor streams of lava (Quart, [own. 

 Geol. Soc. , vol. XXX. p. 220). 



In 1SS8 Sir A. Geikie communicated his elaborate monograph 

 on the history of Tertiary volcanic action in Britain to the Royal 

 Society of Edinburgh (Trans. Roy. Soc. Edin., vol. xxxv., part 

 2, p. 23), which has been incorporated, with fuller details, in his 

 recent work on "The Ancient Volcanoes of Great Britain." 

 His main conclusions may thus be briefly stated : (i) The great 

 basaltic plateaux did not emanate from central volcanoes, but 

 are probably due to fissure eruptions ; (2) the basaltic lavas 

 were subsequently pierced by laccolitic masses of gabl)ro, which 

 produced a certain amount of contact alteration on the previously 

 erupted lavas ; (3) the protrusion of masses of granophyre and 

 other acid materials by means of which the basic rocks were 

 disrupted. 



» During the last six years Mr. Harker has been engaged in 

 mapping the central part of the isle of Skye, and in the petro- 

 graphical study of the rocks, the results of which have been 

 summarised in the annual reports of the Geological Survey. .\s 

 regards the basaltic lavas, he finds that while they have been 

 of vast extent the individual flows have been of feeble volume, 

 and show no evident relation to definite centres of eruption. 

 There were two local episodes, however, which took the form of 

 central eruptions ; one represented by a number of explosive 

 outbursts at certain points ; the other, in the basalt succession, 

 gave rise to rhydlitic rocks. 



Mr. Harker further finds that the succeeding plutonic phase 

 of activity, confined in Skj'e to what is now the central moun- 

 tain tract, is represented by three groups of plutonic intrusions, 

 in the following order : peridotites, gabbros and granites. The 

 metamorphism set up in the basaltic lavas near the large 

 plutonic masses presents points of interest, especially the 



