66 REPORT OF NATIONAL MUSEUM, 1918. 



Explorations for the purpose of securing suitable exhibition speci- 

 mens to illustrate stratigraphic geology and paleontology were car- 

 ried on by the curator and assistant curator of paleontology during 

 June, 1917, and in the same month of 1918. The latter was under- 

 taken too late in the year for the entire results to be incorporated in 

 this report. In June, 1917, in the Frederick valley of Maryland, 

 some carefully selected masses of the limestone conglomerate known 

 as Potomac marble and quartz conglomerate were obtained. The 

 special object searched for was a large mass of edgewise conglomerate 

 to illustrate the phenomenon described by Dr. Walcott as intra- 

 formational, and such a specimen was found in a railroad cut near 

 Hagerstown, Maryland. These specimens, together with a large 

 piece of glacial tillite from the Silurian rocks of Alaska, have been 

 mounted on one base, forming a complete exhibit of the subject of 

 conglomerates in general. 



Dr. Bassler then proceeded to Louisville, Kentucky, where he col- 

 lected additional material for enlarging the early Paleozoic coral reef 

 secured in that vicinity in 1916. After some search he succeeded in 

 locating at Elkin a single thick limestone layer showing a geologic 

 unconformity plain enough to be appreciated by the layman, an ex- 

 cellent specimen, 6 feet long and several feet in thickness. The rest 

 of his field trip was spent in the phosphate regions of central Ken- 

 tucky, where, through the courtesy of the United Phosphate & 

 Chemical Co., a few large exhibition rocks illustrating the phos- 

 phatization of limestone and types of fossils in phosphatic strata, as 

 well as many small specimens, were obtained. 



Dr. C. E. Resser, assistant curator, spent two weeks in June, 1918, 

 in a study of the Cambrian and pre-Cambrian rocks of the Lancaster 

 Valley in Pennsylvania. The stratigraphic part of the work resulted 

 in the collection of over 500 specimens of Lower Cambrian fossils, 

 particularly trilobites. A large mass of contorted limestone from 

 the pre-Cambrian rocks was quarried out and shipped to the Museum 

 for exhibition. The Cornwall, Pennsylvania, iron mines were also 

 visited and a set of minerals from that celebrated locality secured. 

 Over 100 hand specimens of magnetite in schist were collected near 

 Marticville, Pennsylvania. 



During the summer of 1917 Mr. Frank Springer maintained a 

 field exploration in charge of his assistant, Mr. Herrick E. Wilson, 

 covering important Silurian areas in southern Indiana. Valuable 

 additions to the collection of fossil Crinoidea resulted from these 

 operations. 



Other explorations from which the division benefited were those 

 carried on under the auspices of the United States Geological Survey 

 by Dr. Edwin Kirk in the Paleozoic rocks of Alaska, and Dr. E. 0. 



