WEAVER: INVERTEBRATE PALEONTOLOGY AND HISTORICAL GEOLOGY 691 



and described according to the binomial nomenclature. This work was important 

 for those who were later concerned with prolilems of taxonomy. The rapid ap- 

 pearance of published descriptions and illustrations of fossils were followed 

 in 1834-1838 by a summary of the known information concerning paleontology 

 and stratigraphy in H. CI. Bronn's Lethaea Geognostica and his Index Palaeon- 

 tologicus in 1848-1849. Tliese works were of fundamental importance to many 

 of the investigations carried on during the middle of the nineteenth century. 

 The Petre facta Germaniae of Goldfuss and Munster carries descriptions and il- 

 lustrations of fossil echinoids, mollusks, corals, and sponges collected largely 

 in Germany. The publication of d'Orbigny's Paleontologie frangaise began in 

 1840 and continued till 1855. It was his intention to include a description with 

 illustrations of all the fossils found in France but it was confined largely to 

 Jurassic and Cretaceous echinoids, brachiopods, gastropods, and cephalopods. 



In North America James Hall had published several monographs on the 

 Paleozoic fossils of New York State but most of his contributions appeared dur- 

 ing the second half of the century. Intensive investigation of Tertiary mollusks 

 was initiated by T. A. Conrad in 1832-1833 in his work on the fossil shells of 

 the North American Tertiary. The first Tertiary fossil collections made on the 

 Pacific Coast were submitted to him for identification and age determination 

 and initiated a series of investigations which have been in progress for over one 

 hundred years. It is of interest to note that Conrad followed the Cuvierian con- 

 cept of species and believed that the fauna of each period of geologic time suf- 

 fered annihilation as the result of climatic and other environmental changes, 

 new faunas being developed in the following period. 



By the middle of the nineteenth century the Cuverian concept that the faunas 

 of each geologic period had no species in common with those which preceded and 

 followed it was gradually abandoned as information became available that tran- 

 sitional genera and species partially filled the gaps and that the time span for 

 each showed great variations. Although d'Orbigny, Agassiz, and others still 

 supported in varying degrees the views of Cuvier, the evidence presented by 

 Bronn that the faunas of each period resulted from the modification of species 

 of the preceding period, together with the uniformitarian ideas advocated by 

 Lyell concerning earth history, laid the groundwork for the gradual acceptance 

 of Darwin's theory of evolution. The prevailing concepts of the more purely 

 biological aspects of paleontology in 1850 were developed largely from the con- 

 tributions of the above-mentioned investigators and thus were laid the founda- 

 tions for a rapidly expanding science of paleontology. 



Historical Geology Before 1850 



The prevailing ideas concerning stratigraphy at the opening of the nine- 

 teenth century largely resulted from the influence of the earlier teaching of 

 A. G. Werner in Germany. Contemporary publications were largely of a de- 

 scriptive nature, with emphasis on places of occurrence, thickness of layers, 

 and mineralogical composition of the rock. The importance of the use of fossils 

 in determining the age of the strata had not been considered. The science of 

 stratigraphy was established in England early in the nineteenth century as the 

 result of detailed field studies by William Smith. Without formal training 



