BARRANDE ON THE TRILOBITE FAUNAS, 31 



tlie doctrine is well-founded ; but its arbitrary extension is suspicious. 

 Authors too frequently indulge themselves in theories not recon- 

 cileable with our present notions, in the hope that they may here- 

 after be made to agree. In the Alps, where it is impossible to deny 

 that metamorphism on a great scale has taken place, it is often dif- 

 ficult even to surmise how and whence the metamorphism has arisen. 

 This will be admitted by all prudent and inquiring observers. 



The " green slates," in their first and most extensive stage of de- 

 velopment, are dark- or mountain -green clay-slate, with more or less 

 disposition to a scaly or crystalline-foliaceous structure. 



The "grey slates" are a dark-grey clay-slate, hard, and sometimes 

 indeed not effervescent, with their surfaces often glittering with 

 narrow plates of mica, &c. 



In the second division of this Part, the author treats of the zone to 

 the south, next to the central zone. Val Trompia, Val Seriana, Val 

 Brembana, the lake of Como, and Brianza, with the country to the 

 west, are described. In this portion the porphyry and granite, the 

 formations of the older limestone and dolomite, the newer limestone, 

 the flysch and tertiary formations, are considered. 



[J. C. M.] 



On Me Three Successive Faunas, distinguished by their peculiar 

 Trilobites, in the Lowest Palaeozoic Rocks. By M. J. 

 Barrande. 



[Leonhard u. Bronn's N. Jahrb. f. Min. u. s. w. 1852, 3 H. p. 257-266.] 



The limits of the successive faunas of the earlier palaeozoic periods 

 appear to me to be well and naturally defined by means of the ver- 

 tical distribution of the Trilobite families. Thus, 1. The First Fauna 

 [Urfauna], which, everywhere that we meet with it — in Bohemia, 

 England, Sweden, and Norway, consists almost entirely of Trilobites ; 

 and of these, the genera that characterize this fauna are also peculiar 

 to it, viz. Paradoxides, Conocephalus {=^Cahjmene, Angelin), OlenuSy 

 Ellipsocephalus, Sao, &c. Only one of these genera (the Agnostus)y 

 and that under different specific forms, passes on to the Second Fauna. 

 Moreover, all the Trilobites of the Urfauna are distinguished by the 

 great development of the thorax in proportion to the pygidium. 



This fauna is not represented in Russia, France, the United States, 

 and Ireland ; where, however, the Lower Silurian groups are much 

 developed. Nevertheless, sooner or later, indications of this fauna 

 may be discovered in other countries than those above-quoted. In 

 England, even, it was discovered but a few years since, and there 

 only in two isolated spots in the Silurian region, viz. in the Malverns, 

 where Professor Phillips first found Olenus, and in North Wales, 

 where the Officers of the Geological Survey * have since discovered 

 Olenus 2indi Paradoxides \ m the slates of the "Trappean group." 



* [Later particulars respecting the palaeontology of these lowest fossiliferous 

 rocks were given by J. W. Salter, Esq., of the Geological Survey, in a paper read 

 before the British Association at Belfast, 1852. — Transl.] 



t [The locality, however, of this is not certain. See foregoing Note. — Transl.] 



