WEAVER: INVERTEBRATE PALEONTOLOGY AND HISTORICAL GEOLOGY 713 



monograph by F. M. Anderson in which many Upper Jurassic and Cretaceous 

 species from the Coast Eanges were described. Later investigations by this same 

 author on Ammonite faunas and their stratigraphic relationships were published 

 by the Geological Society of America. Investigations on the Carboniferous and 

 Triassic Ammonites of western North America and their relation to similar 

 faunas in other parts of the world were published by J. P. Smith, of Stanford 

 University, in 1903 and 1914. The scientific approach to the solution of his 

 problems was patterned after that introduced by Hyatt. The Cretaceous Ammo- 

 nites of the Upper Missouri region were described by F. B. Meek in 1876. Other 

 important contributions on the Jurassic and Cretaceous Ammonites have been 

 made by J. B. Reeside, Jr. 



The Jurassic and Cretaceous Cephalopods of southern Texas and Mexico 

 were studied and described by C. Burckhardt from 1906 to 1912 and the Permo- 

 Carbonifierous Ammonites of the Glass Mountains by E. Bose in 1917. Similar 

 paleontologic and stratigraphic studies in northern Mexico have been made by 

 L. B. Kellum and E. W. Imlay during the past fifteen years. The short contri- 

 butions made by d'Orbigny and von Buch during the first half of the past 

 century to the invertebrate paleontology of South America were followed during 

 the next one hundred years by many papers on the Mollusca, including Ammo- 

 nites. The early investigations on the Cretaceous pointed to certain problems to 

 be studied by later authors. Among these investigators were G. Steinmann, 0. 

 Wilckens, A. Ortmann, C. Behrendsen, H. von Ihering, W. Paulcke, T. W. Stan- 

 ton, H. Gerth, P. Groeber, F. Krantz, A. F. Leanza, and E. Feruglio. 



Arthropoda: The Trilobites, the most primitive group of this phylum, were 

 abundant at the opening of the Cambrian, indicating that their ancestors prob- 

 ably lived in pre-Paleozoic seas, although their remains have not been discovered 

 as yet. The name was introduced by Walch in 1771 (1768-1771, 3:120), and 

 papers by J. W. Dalman in 1827, F. Quenstedt in 1837, Goldfuss in 1843, Bur- 

 meister in 1843, and H. F. Emmrich in 1845 proposed technical names for the 

 different parts of the exoskeleton which were used for classification purposes. 

 These include the number of thoracic segments, the character and position of 

 the facial sutures, the shape and nature of the glabella, the presence or absence 

 of eyes, structural differences, and the ability of the animal to enroll. In 1852 

 an important monograph by J. Barrande dealing with Silurian Trilobites ap- 

 peared in which all the morphological characters of the exoskeleton were con- 

 sidered and certain phylogenetic relations pointed out. E. Billings in 1870 dis- 

 covered appendages on the ventral side of the genus Asaphus in Silurian rocks 

 and by 1950 similar fossil remains were obtained from Triartlms, Neolenus, 

 Calymene, Ceraurus, and Isotelus. The monograph on British Trilobites by J. W. 

 Salter and H. Woodward, published from 1867 to 1884, is important in that 

 the authors take into consideration the dominant values in ontogeny as a basis 

 for their classification. C. E. Beecher's paper on "Outlines of a Natural Classi- 

 fication of Trilobites," published in 1897, employs the phylogenetic concepts 

 earlier offered by Hyatt and proposes a classification based on the morphogene- 

 sis of all parts of the carapace. He considered the Trilobites especially suitable 

 for the application of the recapitulation theory because of their long history 

 back to the opening of the Cambrian, their generalized structure, and the in- 

 formation available concerning their ontogeny. In an earlier paper on the larval 



