BUFFALO SOCIETY OF NATURAL SCIENCES 9 



known species of eurypterids throughout the world; B, the horizons 

 in which the remains occur, with particular reference to the facies 

 exhibited and to the exact stratigraphical position; C, the mode of 

 occurrence of the remains, whether well preserved or fragmentary, 

 whether a single fragment or a large number of individuals; and 

 finally, D, the other fossils, if there are any, which occur associated 

 with the eurypterids. These facts are all summarized in tables 

 I-III on pp. 37-49 and in the list of faunal associates on pp. 84-91. 

 The second chapter is a resume of the various opinions which have 

 been held regarding the habitat of the Eurypterida. The next three 

 chapters (III, IV and V) deal with the three chief lines of evidence 

 which may be adduced to determine any fossil habitat, namely, -the 

 bionomic characters of the faunas, the lithogenesis of the formations 

 in which the remains occur, and the type of migration and dispersal, 

 marine or fluviatile, indicated by the relations existing between species 

 and genera in synchronous faunas and by the phyletic relationships 

 in successive horizons. In these three chapters general principles are 

 first discussed and criteria are established for recognizing various 

 types of habitats, sediments, and fossil faunas; the application of 

 these criteria to the eurypterid problem is then given in detail. 

 The conclusion reached by the author after the study of all avail- 

 able data and in the light of manifold theoretic considerations is that: 

 the eurypterids throughout their entire phylogenetic history lived in the 

 rivers. 



Aside from the work done on the literature, a large amount of 

 material has been studied, including hundreds of typical specimens of 

 eurypterids, thin sections of some of the waterlimes, the collections 

 of the rock types from the eurypterid-bearing horizons of Europe col- 

 lected by Professor A. W. Grabau and now in the Palaeontological 

 Museum of Columbia University; further, a number of the best sec- 

 tions in the field have been visited. When the present paper was 

 nearly finished there appeared Clarke and Ruedemann's exhaustive 

 Monograph on the Eurypterida of New York (39), which, with Wood- 

 ward's Monograph of the British Fossil Crustacea, gives us the most 

 illuminating and comprehensive work ou the Eurypterida. Many 

 important points in the ontogeny and phylogeny of the eurypterids 

 are here set forth for the first time, and all of the North American 

 species are described in .great detail and figured in a volume of plates 

 that surpass all former illustrations. 



