Principal Literature, Cambrian to Pleistocene.-^- A few of the major contributions to our knowledge of the life of the Palaeozoic are: Cambrian Geology and Palaeontology (1910) and Cambrian Brachiop- oda (1912) by Charles D. Walcott; Cambrian Fossils of Spiti (1915) and other papers on the Palaeozoic of India by Cowper Reed; A Monograph of British Cambrian Trilobites (1906) by Philip Lake, and A Monograph of British Graptolites (1901) by Gertrude Elles and Ethel Wood. The foraminifera have been treated by E. Schell- wien, Monographic der Fusulinen (1908-12); the bryozoa by R. S. Bassler, Early Paleozoic Bryozoa of the Baltic Provinces (1911) and G. W. Lee, British Carboniferous Trepostomata (1912); the echino- derms by R. T. Jackson in his memoir on the Phytogeny of the Echini with a Revision of Palaeozoic Species (1912), and by Frank Springer in his monograph Crinoidea Flexibilia (1920) and in numerous shorter contributions. The ancient arthropods, including, besides the trilobites, merostomes and other arachnids and also insects, have been described by J. M. Clarke and R. Ruedemann in their memoir on The Eurypterida of New York (1912), by Alexander Petrunkevitch, A Monograph of the Terrestrial Palaeozoic Arachnida of North America (1913), by R. I. Pocock, A Monograph of the Ter- restrial Carboniferous Arachnida of Great Britain (1911), and by F. Meunier, Nouvelles recherches sur quelques insectes du terrain houiller de Commentry (Allier) (1906-12). The literature on the Mesozoic contains more references to ammonites than to other groups, be- cause of their abundance and palaeontological importance. The ammonite faunas of the Triassic have been described by James P. S,mith, The Middle Triassic Marine Invertebrate Faunas of North America (1914) and by Carl Diener, The Trias of the Himalayas (1912), Japanische Triasfaunen (1915), and other papers on the Triassic of the Himalayas and southern Europe (1915).
For the Jurassic there are the classic volumes by S. S. Buckman, Yorkshire Type Ammonites (1909-19) continued in the Type Am- monites (1920) and the memoir by C. Burckhardt, Faunes Juras- siques et Cretaciques de San Pedro del Gallo (1912) for Mexico. The studies on Cretaceous ammonites have been more local in character and include: E. Stolley's Beitrdgezur Kenntnissder Cephalopoden der norddeutschen unteren Kreide (1911-2), D. N. Sokolov's Zur Am- moniten Fauna des Petschoraschen Jura (Russian) (1912), H. Yabe and S. Shimizu's, Notes on Some Cretaceous Ammonites from Japan and California (1921), and numerous papers by A. de Grossouyre, W. Kilian and E. Haug for France and the Mediterranean region. The silicious sponges which are so well represented in the Mesozoic have received the most careful microscopic study by the students and followers of Zittel. Pioneer work was done in England by the late George Jennings Hinde, A Monograph of the British Fossil Sponges (1887-19127, and this work was followed in Germany by A. Schrammen's Kieselspongien der oberen Kreide von Nordwest- deutschland (1910) and R. Kolb's Die Kieselspongien des schwdbischen weissen Jura (1911). Special works on other groups are: A Mono- graph of the Cretaceous Lamellibranchia of England (1899-1912) by Henry Woods, Synopsis des Spirobranches (Brachiopodes) Jurassiques Celto-Souabes (1915-^) by the Swiss palaeontologist Louis Rollier, and Clarke and Twitchell's The Mesozoic and Cenozoic Echinodermata of the United States (1915). Among the major con- tributions to Mesozoic stratigraphy and entire faunas or floras may be mentioned: Victor Uhlig s The Fauna of the Spiti Shales (1903), Carl Renz's Die mesozoischen Faunen Griechenlands (1911), G. R. Wieland's American Fossil Cycads (1906-16), and E. W. Berry's The Upper Cretaceous Floras of the World (1916).
For the Tertiary life especial reference should be made to the con- tributions on different groups made by Thomas Wayland Vaughan (corals), E. W. Berry (plants), J. A. Cushman (foraminifera), R. T. Jackson (echinoderms), Mary Rathbun (crustaceans), A. Pilsbry (cirripedia), and others in Contributions to the Geology and Paleontology of the Canal Zone, Panama, and Geologically Related Areas in Central America and the West Indies (1919). The bryozoa have been carefully described and beautifully illustrated by Ferdi- nand Canu and Ray S. Bassler, North American Early Tertiary Bryozoa (1920), while the foraminifera have' been described in equal detail by Joseph A. Cushman in numerous contributions, and by H. Yabe (1921) and H. Douville (1911). For other groups we may note: J. Lambert's Description des Echintdes des terrains neogenes du bassin da Rhone (1911-6), F. W. Harmer's The Pliocene Mollusca (1914-20), and papers by W. H. Dall on the mollusca. A general resume of the Pleistocene vertebrate and invertebrate life is embodied in F. C. Baker's The Life of the Pleistocene or Glacial Period (1920). Stimulat- ing general reviews of the progress of invertebrate palaeontology are the presidential addresses by F. A. Bather, Fossils and Life, British Association (1920), by Ruedemann, The Palaeontology of Ar- rested Evolution (1916), and by Clarke, The Philosophy of Geology and the Order of the State (1917).
PROGRESS IN VERTEBRATE PALAEONTOLOGY Personnel: Advent of the Fourth Generation. The principal feature of the decade has been the advent of a new generation of explorers and workers in vertebrate palaeontology who, in a sense, constitute a fourth or " 2oth century " group. Beginning with Cuvier (1760-1832) as founder of the science and leader
of the first group, the second group embraced the British anato- mists Richard Owen (1804-1892) and Thomas Henry Huxley (1825-1895), the French leader Albert Gaudry (1827-1908), the Swiss palaeontologist Ludwig Rutimeyer (1825-1895), and the three great Americans, namely, Joseph Leidy (1823-1891), Edward Drinker Cope (1840-1897), and Othniel C. Marsh (1831-1899). These men marshalled the first positive proofs of vertebrate evolution in Europe and America; they worked more or less independently as pioneers and laid the entire foundation of the modern classification of the Vertebrata. The leader of the third group was the Russian, Waldemar Kovalevsky (1842- 1883), who instituted intensive investigation of mechanical adap- tation in relation to natural selection. Still productive members of the same period are Arthur Smith Woodward (b. 1864) and Charles W. Andrews (b. 1866) in England, Marcellin Boule (b. 1861) and Charles Deperet (b. 1854) in France, Louis Dollo (b. 1857) in Belgium, Max Schlosser in Germany, Giovanni Ca- pellini(i833- ) in Italy, and in America William B.Scott (b. 1858) and Henry Fairfield Osborn (b. 1857). This group includes also Samuel Wendell Williston recently deceased (1852-1918), and Ramsay H.Traquair (1840-191 2). Scott treated chiefly mammals, Williston chiefly reptiles and amphibians, Osborn both mammals and reptiles. The principal accomplishment of this third school has been (i) to conduct world-wide exploration, (2) to correct, co- ordinate and firmly establish the great classifications proposed by the second school and (3) to fill out the details and principles of phylogeny or lines of reptilian, avian and mammalian descent. The leading explorer of this period was John Bell Hatcher (1861- 1904), who brought together a large part of the materials for two great monographs of the United States Geological Survey, Os- born's TitanotlicrcsanA the Hatcher-Lull C"a,' he also made the wonderful collection of South American fossils which forms the basis of Scott's monumental memoirs of the Princeton University Expeditions to Patagonia during the years 1896-9. Osborn's monograph The Titanothcres (an Eocene-Oligocene family of mammals), twenty-one years in preparation, has been completed but not published; others of his memoirs are the Equidac of the Oligocene, Miocene, and Pliocene of North America (1910) and Camarasaurus, Amp/iicoelias, and other Sauropods of Cope (1921). Williston's monographs are chiefly on the Cretaceous mosasaurs and the archaic Reptilia of the Perm-Trias, to which he made most notable contributions. Of this period were Flor- entine Ameghino (1854-1911), the distinguished vertebrate palaeontologist of Argentina, and Eberhard Fraas (1862-1915) of Stuttgart. Oliver P. Hay (b. 1846) is also of this group, author of the monograph of the Fossil Turtles of North America (1008) and of the invaluable Bibliography and Catalogue of the Fossil Vcrtebrala of North America (1902).
To the fourth group of vertebrate palaeontologists belongs the school trained by Professor Osborn in the American Museum of Natural History, of which the senior is William Diller Matthew (b. 1871), Walter Granger (b. 1872), Barnum Brown (b. 1873), William K. Gregory (b. 1876), Richard S. Lull (b. 1867), of Yale University, Lawrence M. Lambe (1863-1919), late of the Cana- dian Survey, and C. Forster-Cooper, Cambridge University. The chief intensive work of Matthew and Granger has been on the American Eocene mammalian faunas and in aiding Osborn to establish sixteen Eocene-Oligocene life zones of North America very closely coordinated with corresponding life zones of west- ern Europe. Brown's explorations have added greatly to our knowledge of Cretaceous dinosaurs. Of the same group are the pupils of Williston, of whom the leader is Ermine C. Case (b. 1871), who has contributed treatises on Permian life. At the same time John C. Merriam (b. 1869) has led explorations on the Pacific coast of America and inspired a school of younger workers both in vertebrate and invertebrate palaeontology. In Great Britain D. M. S. Watson (b. 1886) has taken up the work of Owen and Huxley in primary groups of fishes, amphibians and reptiles; in Austria Othenio Abel, a pupil of Dollo, is the great exponent of vertebrate evolution; in Germany Friedrich von Huene and Ferdinand Broili are leaders in sauropsidan palaeontology, other notable palaeontologists of recent years being Franz Dre-
