6 HISTORY 



mistake of grouping the Trilobites according to the pattern of their tail-fringes, instead of 

 following Emmerich's natural arrangement, was committed in presence of such materials 

 as Emmerich probably never saw ! 



Angelin's first instalment of the Swedish Trilobites, appeared in IS 52, after many 

 memoirs by Beyrich, and Loven, and Kutorga, and Volborth, on the Swedish or Russian 

 forms ; but it is impossible to notice all the works that followed Emmerich's essay. M'Coy, 

 and Fletcher, and Prof. Wyville Thomson, and myself, have done our best, as opportunity 

 offered, to illustrate the British forms after Portlock's model in 1843. The Decades of the 

 survey by E. Forbes and J. W. Salter appeared in 1849 and 1853. In the last-named 

 year, M. Barrande's long-expected volume made its appearance, and in its illustrations and 

 descriptions of 250 Trilobites is a work without a rival. He is now preparing the second 

 volume, which will add some fifty or sixty more. But as he will be referred to in 

 every chapter that follows, it is not necessary to say more of his work here. On one 

 point only has the author left the field open. He has honestly and modestly stated that 

 he does not profess to classify the Trilobites ; and on this point we are therefore free to 

 follow Dr. Emmerich as before. 



The years 1855 to 1863 have seen great additions to our knowledge of Trilobites made 

 from all quarters : the primordial zone has yielded up its treasures to the search of English 

 and American geologists, and has received additions from all parts of North Europe. 



A formation utterly unknown to science till Barrande established its history 

 has proved to be a most extensive and rich repository for Trilobites. Barrande in 

 Bohemia and Spain, Angelin in Sweden, myself in Britain, — Logan and Dale Owen, and 

 Billings, and more lately James Hall, in the New World, have contributed materials from 

 this most ancient zone of life — the Cambrian. And if of late years systematic classifi- 

 cation has not kept pace with the description of the forms, the fault has not been with 

 the palasontologist in neglecting to supply the data. 



Geological Place.' — The geological history of the Trilobite group is very clear and 

 succinct. Though not the oldest animal forms known, they meet us in the earliest forma- 

 tion in which we have any abundant traces of marine life, viz., the Lingula-flags 

 (Cambrian of Sedgwick, Upper Cambrian of Lyell, Lowest Silurian of Murchison). 



In this their commencement we have some of the smallest and most rudimentary, as 

 well as some of the largest forms ; but the group did not attain its maximum, nor rise to 

 its most perfect forms, till the period of the Llandeilo and Caradoc formations — the 

 typical Lower Silurian deposits. 



Above this point few new types were introduced ; and though individuals were 

 numerous and species most abundant, there were fewer genera in the Upper than in the 

 Lower Silurian. In the Devonian the reduction went still further. In the Carboniferous 

 Limestone they were reduced to three genera ; and the group was extinct before the later 

 portion of the Coal-period. 



As the Trilobites will be constantly referred to the special groups of beds in which 



