36 



NATURE 



[May g, 1872 



In 1S54 Angelinpuljlished his r,il,roiilolo!o!;ii-a SiniiJiiicn'i,a, 

 part 1, Vriistacwt frynialioyth lrtVisitio}:is {\lo, forty-one plates), 

 in wliicli hecilvidetl tlie series of transition rocks above described 

 by Hisinij;er into eight parts designated by Roman numerals, 

 counting'from the base. Of these I. was named Ju-gio FiicoiJaniiii, 

 no organic remains other than fucoids being known therein ; while 

 the remaining seven were named from their characteristic genera 

 of trilobiles, which were as follows, in ascending order ; certain 

 letters being also used to designate the parts : — II. (A) Olcnus : 

 III. (B) Conocoryphc ; IV. (BC) Ceratopyge ; V. (C) Asaphus ; 

 VI. (D) Trinucleus; VII. (DE) Harpes ; VIII. (E) Cryptony- 

 mu3. In the /t'fj.'/o O'.ciwrum (II.) was found also the allied genus 

 ParatliKxuies. \Vith regard to the characteristic genus of Regio 

 III., the name of CotiMoiypJie wa<; proposed for it by Corda in 

 1847, as synonymous with Zenker's name of Conpci-pltnliis {Coiio- 

 n-f'/ialitis), already appropriated to a genus of insec's. 



Meanwhile the similar crustaceans which abnundinthe tran- 

 sition rocks of Bohemia had been studied and described by 

 Ilawle, Corda, and iJeyrich, when r,arrande began his admirable 

 investigations of this ancient fauna and of its stratigraphic.il re- 

 lations, lie soon found that beneath the horizon characterised 

 by fossils of the ISala group (Llandeilo and Caradoc) there ex- 

 isted in Bohemia a series of strata distinguished by a remarkable 

 fauna, entirely distinct from anything known in Great Britain, 

 but closely allied to that of the alum slates of Scandinavia, cor- 

 responding to Regiones II. and III. of Angelin. To this he 

 gave the name of the first or primordial fauna, and to the rocks 

 yielding it that of the Primordi.il Zone. Resting upon the old 

 gneisses of Bohemia appears a series of crystalline schists des'g- 

 nated by Barrande as Elagt A, overlain by a series of sandstones 

 and conglomerates, E/agi- B, upon which repose the fossillfrrous 

 argillites of the Primordial Zone or E/nge C. The rocks of the 

 Eta"es A and 1! were by Barrande regarded as azoic, but in 

 1 86 1, Eritsch of Prague, after a careful search, discovered in 

 certain thin-bedded sandstones of B the traces of fiUedup vor- 

 tical double tubes ; which, according to .Salter (Mem. Geol. Sur, 

 iii. 243), are probably the marks of annelides, and are identical 

 with those found in the rocks of the Bangor or Longmynd group 

 in Great Britain ; which will be shown to belong to the Primordial 

 Zone. It is, therefore, probalile that the Etage B, which appar- 

 ently corresponds to the Regio Fucoidarum or basal sandstone 

 of Scandinavia, should itself be included in the Primordial Zone. 

 It may here be noticed that it is in the crystalline schists of A 

 that Gumbel has found Iukooii bavariciim. To the Etage C in 

 Bohemia, Barrande assigns a thickness of about 1,200 feet, and 

 to this his first fauna is confined, while in the succeeding divisions 

 he distinguished a second and a third. The second fauna, whicli 

 characterises Etage D, corresponds to that of the Bala group ; 

 while the third fauna, belonging to the Etages E, F, G, and H, 

 is that of the M.ay Hill, Wenlock, and I.udlow formations of 

 Great Britain. 



This classification of the ancient Bohemian faunas was first set 

 forth by Barrande in 1846, in his A^oticc Priiiiiibuiirc, in which 

 he declared that the first fauna was below the base of the Llan- 

 deilo of Murchison, unknown in Great Britain, and, moreover, 

 " new and independent in relation to the two Silurian faunas 

 (his second and thiid) already established in England." This 

 opinion he reiterated in 1859. These three divisions form in 

 Bohemia an apparently continuous series, and bemg connected 

 with each other by some common species, Barrande was led to 

 lojk upon the whole a.-i forming a single stratigraphical system ; 

 and finally to assert that these three independent faunas " form 

 by their union an inilivi-ible triad which is the Silurian system." 

 (liul. Soc, Geol.de Fr. II. xvi. 529-545.) Already, in 1852, in 

 his magnificent work on the Silurian System of Bohemia, Bar- 

 rande had given to the strata characterised by his first fauna 

 the name of Primordial Sdurian. It is difficult to assign any 

 just reason for thus annexing to the Silurian— already augmented 

 bv the whole Upper Cambrian or Bala group of Sedgwick, 

 (Llandeilo and Caradoc) — a great series of^ fossiliferous rocks 

 lying below the base of the Llandeilo, and unsuspected by the 

 author of the Silurian system ; who persistently claimed the Llan- 

 deilo beds, with their characteristic second fauna, as marking the 

 dawn of organic life. 



Up to this time the primordial pala-ozoic fauna of Bohemia and 

 of Scandinavia was, as we have said, unknown in Great Britain. 

 The few organic remains mentioned by Sedgwick in 1S35 as 

 occurring in the region occupied by his Lower and Middle Cam- 

 brian, on Snowdon, were found to belong to Bala beds, which 

 there rest upon thi older rocks ; nor was it uii'il 1S45 that Mr. 



Davis found in the Middle Cambrian remains of Liitgnla. In 

 1846, Sedgwick, in company with Mr. Davis, re-examined these 

 rojks, and in December of the same year described the Lingula 

 beds as overlaid by the Tremadoc slates and occupying a well- 

 defined horizon in Caernarvon and Merionethshire, beneath the 

 great mass of the Upper Cambrian rocks. (Geol. Jour. ii. 75, 

 iii. 139.) .Sedgwick, at the same time, noticed about this 

 horizim certain Graptolites and an Asapliiis, which were supposed 

 to belong to the Tremadoc slates, but have since been declared 

 by .Salter to pertain to the Arenig or Lower Llandeilo beds, the 

 base of the Upper Cambrian. (Mem. Geol. Sur. iii. 257, 

 and Decade II. ) 



This discovery of the Lingula flags, as they were then named, 

 and the fixing by Sedgwick of their geological horizon, was at 

 once followed by a careful examination of them by the Govern- 

 ment surveyors ; and in 1847, Sclwyn detected in the Lingula 

 fljgs, near Dolgelly, in Merionethshire, the remains of two 

 crustacean forms, the one a phyllopod, which has received the 

 name of Hymcnocaris verDiicaitda .Salter, and the other a trilo- 

 bite, which was described by Salter in 1S49 as Olciins iiiiirwus. 

 (Geol. .Survey, Decade II.) A species oi ParadoxiJcs, apparently 

 idtntical wi'h P. Forchaiiimeri of .Sweden, was also about this 

 time recognised among specimens supposed to be from the same 

 horizon. It has since been described as P. I/icksii, and found 

 to belong to the basal beds of the Lingula Hags — the Menevian 

 group. 



Upon the flanks of the Malvern Hills there are found resting 

 upon the ancient crystaUine rocks of the region, and overlain 

 by the Pentamerus beds of the May Hill sandstone (originally 

 called Caradoc by Murchison) a series of fossiliferous beds. 

 These consist in their lowest part of about 600 feet of greenish 

 sandstone, which have since yielded an Oholella and Scrpiiliks, and 

 are overlain by 5C0 feet of black schists. In these, in 1S42, 

 Prof John Phillips found the remains of trilobites, which he sub- 

 sequently described, in 184S, as three species of Oh'iiiis (Mem. 

 Geol. Survey ii. part I, 55). These black shales, which had 

 not at that time furnished any organic remains, were by Murchi- 

 son in his " Silurian System" (p. 416) in 1839 compared to the 

 supposed passage beds in Caermarthenshire between the Llan- 

 deilo and the Cambrian (Bala) rocks ; which, as we have seen, 

 were newer and not older strata than the Llandeilo flags. From 

 their lithological characters, and their relations to the Pentamerus 

 beds, these lower fossiliferous strata of Malvern were subsequently 

 referred by the Government geologists to the horizon of the 

 Caradoc proper or Bala group ; nor was it until 1S51 that their 

 true geological age and significance were made known. In that 

 year, Barrande, fresh from the study of the older rocks of the 

 Continent, came to England for the purpose of comparing the 

 British fossils with those of the Primordial Zone which he had 

 established in Bohemia and Scandinavia, and which he at once 

 recognised in the Lingula flags of Sedgwick and in the black 

 schists at Malvern ; both of which were characterised by the pre- 

 sence of the genus Olcnus, and were referred to the horizjii o. his 

 Etage C. This important conclusion was ann ninced f>y .Saltir 

 to me British Association at Belfast in 1852 (Rep. Brit. Assoc, 

 abstracts, p. 56, and Bull. Soc. Geol. de I'r. II. xvi. 537). 

 Since that time the progress of inve.'tigation in the Middle and 

 Lower Cambrian rocks of Wales has shown a fauna the 

 importance and richness of which has increased from year 

 to year. 



The palo^ontological studies of Salter, while they confirmed the 

 primordial character of the whole of the great mass of strata 

 which make up the Middle Cambrian or Festiniog group of 

 Sedgwick (consisting of the Lingula flags and the Tremadoc 

 slates), led him to propose several sub-divisions. Thus he dis- 

 tinguished on pala:ontological grounds between the upper and 

 lower Tremadoc slates, and for like reasons divided the Lingula 

 flags into a lower and an upper portion. For the discussion of 

 these distinctions the reader is referred to the memoirs of the 

 Geol. Survey (iii. 240-257). Subsequent researches led to the 

 division of the original Lingula flags into three parts, an upper 

 and a mldd'e, to w hich the names of Dolgelly and Maentwro" 

 were given by Mr. Belt, and a third consisting of the basal bed^ 

 which were separated in 1865 by Salter and Hicks, with the 

 designation of Menevian, derived from the ancient Roman name 

 of St. David's in Pembrokeshire. It was here that in 1862, 

 Salter found Pnrado.xh/cs with Agtins/iis and Liii^ithi in fine 

 black shales at the base of the Lingula flags, resting conformably on 

 the green and purple grits of the Lower Cambrian or Hariech 

 beds. The locality was afterwards carefully studied by Hicks, 



