22 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



found in the calcareous slates and flagstones of Solenhofen. 

 The first half of the second volume contains illustrations of 

 molluscs, brachiopods, and echinids, and the descriptive text 

 by Walch embraces practically all that was known in the 

 previous literature about these fossils ; in the second half the 

 same treatment is given to so-called " corallioliths " (sponges 

 and corals), to encrinites (crinoids), to osteoliths (fossil 

 bones), to belemnites, dentalites, vermiculites, and balanoids. 



The third volume begins with a dissertation about fossil 

 wood, followed by the description of a number of Carbon- 

 iferous plants. The chapter on the fossil Crustaceans which 

 received the name of "Trilobites" from Walch, ranks far 

 above all previous descriptions of these interesting fossils. 

 The remainder of this volume is devoted to the description 

 of supplementary plates. The fourth volume contains a 

 systematic summary of all fossil forms treated in the 

 foregoing volumes. The masterly text of Walch sets forth 

 his own original observations, and displays a knowledge 

 of the older literature unsurpassed for its completeness and 

 accuracy. 



With the exception of Knorr and Walch's important work, 

 palgeontographical literature up to the middle of the eighteenth 

 century stands on a low scientific level. This seems the more 

 remarkable when one compares the formal descriptions of 

 fossils, and speculations about their origin and their scrip- 

 tural significance, with the well-directed efforts of botanists 

 during the same period. Botanists had already brought the 

 systematic arrangement of plants to such a point that only 

 the nomenclature of Linnaeus was required to make it serve 

 as a secure basis for the further progress of research. But so 

 far, in the kindred study of the history and classification of 

 animals, no fundamental principles had been attained. It 

 is true some of the more advanced writers, such as Hooke, 

 had said that certain fossil species might possibly be extinct 

 forms. Yet, when from time to time ammonites, trilobites, 

 crinoids, and other fossils were found which had no known 

 existing counterparts, the authorised treatment was to take for 

 granted there might be living representatives existing at depths 

 or in regions of the ocean hitherto unexplored. 



Interest centred in the chimeric hope of finding living 

 specimens of these mysterious fossils, and no observer had yet 

 conceived the far bolder, grander dream of defining successive 



