REPORT OF THE SECRETARY. 7 



MASTODON FROM INDIANA. 



Many finds of mastodon and mammoth remains, especially from 

 different localities in States bordering on the Great Lakes, are con- 

 stantly being reported to the Institution. These " finds," chiefly in 

 swamp deposits of the Pleistocene, generally consist of a few isolated 

 bones or teeth, but afford evidence of an abundance of these great 

 creatures during the geological age just preceding the present. Com- 

 pared, however, with the great number of remains found, complete 

 skeletons are rare, principally because the finds are generally brought 

 to light by workmen who have little or no knowledge of the scien- 

 tific value of the remains. The National Museum was therefore 

 fortunate during the past year in the acquisition of a fine, nearly 

 complete adult male mastodon skeleton from a swamp deposit in 

 northwestern Indiana. 



A part of the skull, four limb bones, a few ribs and vertebrae 

 were unearthed by a dredge crew while excavating a drainage canal 

 and shipped to the Institution. Mr. J. W. Gidley, of the National 

 Museum, later succeeded in finding the lower jaws, most of the re- 

 maining vertebrae and ribs, parts of the pelvis, and a few more limb 

 and foot bones, and on a second visit found the missing sections of 

 the vertebral column, several more foot bones, and other important 

 fragments. On assembling all the bones recovered it has been found 

 that, with comparatively little artificial restoration, an unusually fine 

 and complete specimen of the American mastodon can be prepared 

 for exhibition. 



PALEONTOLOGICAL AND STRATIGRAPHIC STTJDIES IN THE PALEOZOIC ROCKS. 



Dr. E. O. Ulrich of the National Museum, was occupied for sev- 

 eral months during the field season of 1915, under the auspices of 

 the United States Geological Survey, in a study of the lower 

 Paleozoic deposits of the Mississippi Valley. He was engaged 

 chiefly in seeking evidence respecting the boundary line between the 

 Cambrian and Ozarkian systems. For this purpose many of the 

 outcrops of these rocks were visited, but the most important evidence 

 was found in the upper Mississippi Valley and in the Missouri where 

 the Upper Cambrian rocks are particularly well displayed, and the 

 succeeding deposits of the Ozarkian system are more commonly 

 fossiliferous than elsewhere. The relative abundance of fossils in 

 these areas permitted the actual boundary between the two systems 

 to be accurately determined after considerable study. This boun- 

 dary Avas found to coincide wath the uneven plane formed at the 

 junction of the deposits laid down by the retreating Cambrian sea 

 with those formed by the return of the waters in the succeeding 

 Ozarkian time. During the progress of these stratigraphic studies 



