WEAVER: INVERTEBRATE PALEONTOLOGY AND HISTORICAL GEOLOGY 711 



merous papers appeared between 1915 and 1913 by B. L. Clark on the Tertiary 

 mollusks of the Pacific Coast. Contemporaneously, the faunas of the Eocene were 

 described by R. E. Dickerson (1914) and in 1925 the fauna of the type Tejon 

 was described by F. M. Anderson and G. D. Hanna. In 1926 and 1930 two im- 

 portant monographs involving a detailed morphologic and systematic study of 

 Gabb's types from California were published by Ralph Stewart. This work set 

 the standard for more critical reviews of the generic nomenclature of fossil mol- 

 lusks in many of the investigations which followed. A monograph dealing with 

 a detailed systematic study of the mollusks of the Pliocene and Pleistocene of 

 California was published by U. S. Grant IV and Hoyt Rodney Gale in 1931. 

 Investigations of the species of particular genera such as Acila, Nucula and 

 Yoldia, undertaken by TI. G. Schenck at Stanford University during the second 

 quarter of the century, pointed out the desirability of research on special generic 

 groups. A very valuable catalogue was published by A. Myra Keen and Herdis 

 Bentson in 1944 on all of the known Tertiary molluscan species in California. 



Cephalopoda: The Cephalopods represented by both living and fossil groups 

 were studied, described, and classified in different ways during the first half of 

 the nineteenth century, but the vast literature which has accumulated concern- 

 ing this class during the past one hundred years has revealed a fairly clear knowl- 

 edge of their morphologic relationsliips. The living Nautilus, the cuttlefisli, and 

 Foraminifera were placed in the class Cephalopoda in 1798 by Cuvier and con- 

 sidered distinct from all other mollusks. In 1801 Lamarck noted the differences 

 in the suture lines between Animoiiites and Nautilus and in 1825 De Haan clas- 

 sified the known genera under three families — Ammonitea, Goniatites, and Nau- 

 tilea. Owen in 1832, in a paper on the soft anatomy of the genus Nautilus, 

 pointed out its relation to the Cephalopoda and divided that class into two 

 orders, Tetrabranchiata and Dibranchiata, placing tlie living genus in the former. 

 Von Buch, in papers published between 1829 and 1849, divided the Cephalo- 

 pods into the Nautilidae and Ammonitidae largely on the position of the si- 

 phuncle, and separated the Ammontidae into three sections — Goniatites, Cera- 

 tites, and Ammonites. He introduced technical names for the different parts of 

 the suture lines and used these, along with the varying shape and decoration 

 of the shell, for the establishment of fourteen families. Observations made on 

 the shells of many genera from the Paleozoic through to the end of the Mesozoic 

 showed a progressive complication of the suture lines prophetic of future phylo- 

 genetic investigations. The new avenues of approach for the study of Cephalo- 

 pods formed the groundwork for this type of research between 1850 and 1950 

 and resulted in the appearance of an extensive literature concerning the phylo- 

 genetic relationships of Paleozoic and Mesozoic genera. 



Among the more important contributions to the study of the Cephalopoda 

 at the opening of the second half of the last century were the works of F. A. 

 Quenstedt on Der Jura in 1858 and Die Ammoniten des Schivdhischen Jura 

 from 1885-1888. The monographs of Pictet and Campiche from 1858 to 1864 

 contain descriptions of the Cretaceous Cephalopods of Switzerland and those 

 of J. Barrande (1852-1889) the Silurian Nautiloids of Bohemia. The morpho- 

 logical studies by Suess (1866) showed that, in addition to the details of the 

 suture lines, the variations in the size of the chambers and the shape of the aper- 

 ture were of importance in classification. With the use of these additional char- 



