268 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



Geological Survey in the Appalachians of eastern Tennessee. In 

 Illinois and Kentucky the work of the respective State surveys was 

 used. From Tennessee through North Carolina to Pimlico Sound 

 and the Atlantic Ocean, the section of W. C. Kerr of the North 

 Carolina Geological Survey was followed. 



The horizontal scale is 2 miles and the vertical 4,000 feet to the 

 inch. In order that the geologic structure might be better shown, 

 the lower line of the section was carried 5,000 feet below. sea level. 



The section is especially interesting in that it illustrates the rela- 

 tion between geology and geography. For example, the low lying 

 Atlantic Coastal Plain is seen to be formed of horizontal uncon- 

 solidated sands and clays of comparatively recent origin ; the higher 

 Piedmont Plateau is underlaid mainly by greatly contorted and 

 deeply eroded igneous rocks; the Appalachian Valley is a great lime- 

 stone area ; the Cumberland Plateau of horizontal sandstones, shales, 

 and coal beds, forms the great Eastern coal field ; the Mississippi 

 Valley is composed almost entirely of horizontal Paleozoic rocks, and 

 the Great Plains of Mesozoic and Cenozoic strata. It brings out 

 also in strong contrast the deeply eroded Appalachian areas, where 

 the old mountain ranges are worn down almost to their roots, with 

 the more recently uplifted and less eroded Rocky Mountains and 

 other still more recent ranges to the west. The Rocky Mountain and 

 Great Basin areas show further numerous volcanoes which have 

 broken through the greatly disturbed and uplifted strata and poured 

 out great lava flows at various intervals. Faulting or dislocation of 

 the strata in this area is plainly evident along the west front of the 

 Wasatch Mountains in Utah, in the Basin Range Mountains, and also 

 along the Coast Range of the Pacific, where occurred the renewal of 

 faulting producing the San Francisco earthquake of 1906. 



Above this structure section various large fossil invertebrate ani- 

 mals are mounted on the wall. Conspicuous among these are several 

 exceptionally large cephalopods, ancestors of the pearly nautilus. 



Biological series. — The biological series contained in special upright 

 cases along the south wall (south or left side, pi. 2, fig. 1) gives a com- 

 prehensive idea of all the different types of invertebrate life of past 

 ages. This exhibit is designed more especially for students and col- 

 lectors. Beginning with the simple one-celled protozoa and proceed- 

 ing with the sponges and corals through all the higher types of 

 invertebrate animals, one or more special cases are devoted to each 

 of the classes. As the structure of the fossil forms is sometimes ob- 

 scure, numerous drawings and photographs are introduced. Of 

 exceptional interest in this series are the fossil sea lilies forming a 

 part of the Frank Springer collection of echinoderms. The method 

 of showing these beautiful petrified remains, which, however, are 



