GEOLOGY IN NATIONAL MUSEUM MERRILL. 269 



animals not plants, as the popular names suggest, is shown in figure 2, 

 plate 3. Another striking object is the largest known Trilobite (iso- 

 telus brachycephalus Foerste) found in 1919 during the work of exca- 

 vating for a dam on the Ohio River near Dayton. The actual size is 

 8 by 15 inches. The detail with which each class of invertebrates is 

 treated is shown in the accompanying illustration of one of the two 

 cases devoted to fossil brachiopods (pi. 4, fig. 2). This case shows also 

 the method of installation of small objects for exhibition purposes. 

 The specimens are fastened to terra cotta tiles by a combination of 

 plaster of Paris and liquid glue and the tiles are mounted between 

 grooves on an upright or slightly sloping frame. 



Faunal exhibits. — This same series of exhibits contains two f aunal 

 collections, one case being devoted to the assemblage of Middle Cam- 

 brian organisms so remarkably preserved in the rocks that the most 

 minute details of their anatomy are preserved. The specimens shown 

 were discovered and collected by the secretary of the Smithsonian In- 

 stitution, Dr. Charles D. Walcott. Another faunal exhibit comprises 

 the Ordovician and Early Silurian fossils of southwestern Ohio. 

 This area is perhaps best known to all students of the science on 

 account of the abundance and perfect preservation of its invertebrate 

 remains. The specimens were selected from a very large number 

 forming the I. H. Harris collection. 



Only a small portion of the collection of fossil invertebrates is 

 on exhibition, the remainder forming a study series distributed in 

 the various offices and workrooms of the Museum under the care of 

 specialists. This study collection, probably the largest of its kind in 

 the world, is contained in about 20,000 standard drawers, 24 by 30 

 inches in size, and includes literally millions of specimens. The 

 number of its type specimens can be judged from a list published in 

 1905, which occupied a volume of 704 pages; since that time almost 

 an equal number has been added. Space will not permit mention of 

 more than a few of the important collections contained in this series. 

 Among them are the Walcott collection of Cambrian fossils contain- 

 ing the results of practically all the researches upon this group of 

 strata; the Ulrich collection of Early Paleozoic fossils with its 

 thousands of type specimens; the Rominger and Nettelroth collec- 

 tions of Silurian and Devonian fossils ; the Frank Springer collection 

 of fossil echinoderms forming the most complete series of this class 

 extant; the Harris collection of Ordovician and Silurian fossils; the 

 "Williams and the Sherwood collections, representing a lifetime of 

 work on the Devonian, and numerous collections of Mesozoic fossils, 

 assembled by Dr. T. W. Stanton and his associates on the Geological 

 Surveys ; a great biological series of Tertiary molluska assembled by 

 Dr. W. H. Dall ; and a similar stratigraphic series of Tertiary forma- 

 tions collected by Dr. T. Wayland Vaughan and his assistants. 



