PREFACE.

Having given a sketch of the plan of my present work in the subsequent introduction,it will be superfluous to enlarge further upon it here. My treatment of this subject in amerely zoological point of view is partly owing to the very natural consideration that these

most ancient remains of the animal world not only admit of such a mode of contemplation,

but, indeed, demand it, if the subject is to be thoroughly worked out; but partly also no

doubt it is to be attributed to the entirely zoological direction of my studies. Works on

fossils are undoubtedly the more profound, the more the author has penetrated into thestudy both of Geology and Zoology; but who, excepting Cuvier , can boast of such a

universality ? I therefore preferred to relinquish the geological investigation of the subjectentirely, and not enlarge on the various strata containing Trilobites, and I would also

request the reader not to lay any great weight on the geological observations he willoccasionally meet with in the course of the work; for they may sometimes have been based

on the views of others imperfectly understood, and for this and other reasons they must

be considered as not to be implicitly relied on. On the other hand, I would venture tohope, that my zoological system of arranging the various groups may meet with the appro-bation of my readers, and that I may have succeeded in my endeavours to lay the foun-

dation of a single and correct view'of the subject, which may supersede the many fluctu-

ating ones hitherto prevailing. My object indeed included both these departments of thesubject, but I cannot answer for the correct designation of many specimens supposed to beof identical species, but frequently no doubt imperfectly determined, or of others presumedto be new, the originals of which I was not permitted to examine. I have indeed receivedmuch assistance from German authors, but have often not been so fortunate with regard tothose whose species appeared to me the most questionable, and in such cases thedetermination was frequently left to the view I took of them on my own personal inspection.I have seen everything connected with my object contained in the collections of Berlinand Halle, and I have also received valuable contributions from Mr. Bocksch in Silesia,from Captain von Charpentier, and from Mr. Honinghaus at Crefeld. On the other

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