REPORT OF DEPARTMENT OE INVERTEBRATE FOSSILS. 205 



Ptychupariu? calj/mtiiuidtx, Whitfield. 



PtyekoparUk sp. I 



A<irauloH ll'ooxftri, Whitfield. Potsdam sandstone, Eau Claire beds, Dunn County, 



Wisconsin. Prom Public Matenm of Milwaukee, Wis., by Mr. Carl Doeillinger, 



secretary. 

 Eurfptenu >t»,ip<x, l>c Kay. A very fine ipeoimeD. Waterlime group, Williams- 



vill., N. Y. From Mr. James Temple Brown, U. S. National Museum. 

 Small miscellaneous collection : 



Carboniferous. From Mi. William K&noher, Oregon, Holt County, Missouri. 



WORK ON COLLECTIONS. 



The direct work on the collections of the Museum bus been the re- 

 cording, identifying, and labeling of the material mentioned under ac- 

 cessions, and a continuation as opportunity offered of the arrangement 

 of the old collections of the Smithsonian Institution. The latter work 

 has been very limited, owing to the writer's position as paleontologist 

 in charge of the Paleozoic paleontology of the U. S. Geological Survey, 

 requiring him and his assistants to devote the most of their time 

 to original work in connection with the Survey. This work will, in a 

 large degree, inure to the benefit of the Museum collections, as the 

 material studied contains many new types and large numbers of spe- 

 cies illustrating the stratigraphic and geographic distribution of life 

 during Paleozoic time. 



RESULTS OF THE WORK ON THE COLLECTIONS FROM NEVADA, AS 

 GIVEN IN MONOGRAPH VIII OF THE U. S. GEOLOGICAL SURVEY. 



"As an assistant geologist in the field work, the writer collected most 

 of the fossils in situ, and studied their mode of occurrence and strati- 

 graphic relations, thus disposing of an element of uncertainty which 

 frequently arises in the mind of the paleontologist when examining col- 

 lections from a region unfamiliar to him, and which presents, in the 

 strata of the lesser divisions of its great geologic series of rock, asso- 

 ciations of species unknown elsewhere, or an unusual vertical range of 

 individual species. 



u The succession in the faunal series from the Olenellus (or Middle 

 Cambrian) fauna, through a large, well-defined fauna of the character 

 of that of the Potsdam group of New York and the Mississippi Valley, 

 to one that in its assemblage of species combines both Cambrian and 

 Silurian types, and passes upward into a fauna comparable to that of 

 the Quebec group or the Calciferous and Chazy groups, is of special in- 

 terest. The transition from the Cambrian to the Silurian fauna is very 

 gradual, and such as would occur where there was no marked physical 

 disturbance to influence the faunal change resulting from the natural 

 dying out and development of species or the influx of new species from 

 other areas. 



"The fauna between that of the Silurian and the Devonian horizons is 

 SO meager that the only reference made to it is in the systematic list and 

 in the lists of the geologic report. (Geology of the Eureka Distiict.) 



