712 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



acters he introduced the new generic names PJiylloceras, Lytoceras, and Arcestes. 

 Contemporaneously in North America new methods were advocated by Alpheus 

 Hyatt (1872) for the study of Cephalopods and by 1869 the earlier nomencla- 

 ture of families was abandoned and a new system erected, which was founded 

 largely on phylogenetic considerations. This early work was followed by nu- 

 merous papers elaborating on the principles outlined, with the description of 

 many sharply defined genera. Among the more important of Hyatt's papers was 

 his "Genera of Fossil Cephalopods" in 1884 and the Genesis of the Arietidae in 

 1889. He introduced the method of study involving a detailed investigation of 

 the successive whorls back to the initial chamber or protoconch and thus at- 

 tempted to unravel the phylogenetic development in terms of the ontogenetic, 

 thereby opening up a new line of research which has been followed by later 

 students. These methods of attack were followed by M. Neumayr on the Am- 

 monites of the Alps and North Germany from 1871 to 1881; Ed. Mojsisovics 

 (1873-1876) on the Triassic of the Alps and on the Upper Triassic of the Hima- 

 layas in 1896; W. Waagen (1879-1895) on the Cephalopods of the Salt Range, 

 India; and K. A. von Zittel on the Stramberger Beds (1868) and on the Titho- 

 nian of the Alpine region in 1870. Neumayr founded his classification of Ce- 

 phalopods on a consideration of direct or close relationship of genera in the line 

 of descent. Others who have added to the information concerning Cephalopods 

 are Thomas Wright (1878-1885) on the Ammonites of the Lias of Great Britain; 

 J. F. Pompeckj (1893-1896) on the Ammonites of Schwabia; A. Karpinsky 

 (1889) on the Permian Ammonites of Russia; W. Branco (1880-1881) on the 

 development and history of fossil Cephalopods; G. G. Gemmellaro (1887-1899, 

 1904) on the Ammonites of Sicily; and A. Fusini (1897) on the Liassic Ammo- 

 nites of the Appenines. 



From 1895 to 1919 C. Diener described the Ammonites of the Himalayan 

 region and published papers on the environment, geographic distribution, su- 

 tures, and living chambers of Ammonites. In 1903 R. Hoernes discussed prob- 

 lems of ontogeny and phylogeny. The North German Ammonites were described 

 in 1902 by A. von Koenen and the Jurassic Ammonites of France in 1910 by 

 Dumortier. Papers by S. S. Buckman appeared from 1887 to 1900 on the Am- 

 monites of the Lower Oolite of Great Britain and his monumental work on the 

 Yorkshire Ammonites in 1909. The fine discrimination of species in this last 

 work has been of fundamental importance to Jurassic stratigraphy. Notable con- 

 tributions to the study of Ammonites during the past twenty-five years have been 

 made by L. F. Spath in England and W. Kilian in France. 



The significant publications of Hyatt in North America were followed by 

 the contributions of numerous authors in the western hemisphere. In 1893 J. M. 

 Clarke discussed the protoconch of OrtJioceras and in 1897 the Lower Silurian 

 Cephalopods of Minnesota. The Ordovician and Silurian Cephalopods were de- 

 scribed by A. F. Foerste in 1921, and other papers dealt with the morphology of 

 Paleozoic genera. These investigations were followed by the important papers 

 of A. K. Miller on nautiloids and Paleozoic ammonites. The families of the Nau- 

 tilidae, Hercoglossidae, and Aturiidae from the Pacific Coast Tertiary were 

 discussed by H. G. Schenck in 1931. In addition to the early papers by Gabb on 

 the Mesozoic Cephalopods of California and Oregon and those of Whiteaves 

 (1876-1903) on the Cretaceous of British Columbia, there appeared in 1902 a 



