310 



REPORT OF NATIONAL MUSEUM, 1893. 



WALCOTT, Charles D.— contiuued. 

 lug Middle Paleozoic time. It is accompanied 

 by three maps, one of which illustrates the 

 relative amount of sedimentation within the 

 typical geologic provinces of North America 

 during Cambrian time. The second is a hypo- 

 thetical map of the continent at the beginning 

 of Lower Cambrian time, and the third is one 

 of the same character, representing the conti- 

 nent at the beginning of Lower Silurian (Ordo- 

 vician) time. Several important conclusions 

 were arrived at. Among them are : 



1. The preCambrian Algonkian continent 

 was formed of the crystalline rocks of the 

 Archean nuclei, and broad areas of superjacent 

 Algonkian rocks that were more or less dis- 

 turbed and exten.sively eroded in i)re-Canibrian 

 time. Its area was larger than at any succeed- 

 ing epoch until Mesozoic time. 



2. At the beginning of Cambrian time three 

 Ijriucipal areas of sedimentation existed: (rt) 

 The Atlantic coast province, including various 

 seas between the several pre-Cambriau ridges; 

 (h) a narrow sea extending along the western 

 side of the Paleo-Appalachian range, from the 

 present site of Labrador to Alabama; (c) a 

 broader sea on the western side of the conti- 

 nent, west of the Paleo-Rocky Mountain 

 ranges, that extended from the southern por- 

 tion of the present site of Nevada northward 

 into liritish Columbia and probably toward the 

 Arctic Circle, and south to the Paleo-Gulf of 

 ^Mexico, and thus connecting with the Paleo- 

 Appalachian Sea. 



3. The Cambrian age began to invade the 

 great interior continental area in late Cambrian 

 time, and extended far to the north toward the 

 close of the period, as indicated on PI. xlv. 



4. The depression of the continent in rela- 

 tion to sea IcTel began in pre-Cambrian time 

 and continued with few interruptions until the 

 close of Paleozoic time. 



5. The relative i)ositions of the contincnta 

 area and the deep seas have not changed since 

 Algonkian time. 



6. The sedinvents of Cambrian time were 

 accumulated to a great extent in approximately 

 shallow seas, except in poi-tions of the Paleo- 

 Rocky Mountain and Paleo-Ajipalachian seas- 



7. The lower Cambrian fauna lived in the 

 seas of the Atlantic coast province, the Paleo- 

 Appalachian and the Paleo-Rocky Mountain 

 seas. 



8. The Middle Cambrian fauna of the Atlan 

 tic basin is not known to have penetrated into 

 the Paleo-Appalachian or Paleo-Rocky Moun- 

 tain seas, except in the case of a few species 

 now found in Alabama and jtrobably eastern 

 New York. The portion of the fauna occupy, 

 ing the same relative stratigrai)hic position in 

 the grouj) is essentially the same as the Paleo. 

 Appalachian and Paleo-Rocky Mountain sec- 

 tions. 



9. The Upper Cambrian fauna was distrib- 

 uted over the broad interior continental area 

 and in the Paleo-Appalachiau and Paleo- liorky 



WALCOTT, CiiARLE.S D.— continned. 



Mountain seas, but it has not been recognized 

 by the same genera and species in the Atlantic 

 coast province, the fauna of the latter being 

 more closely allied to that of the Upper Cam- 

 brian of the eastern side of the Atlantic basin. 



Notes on the Cambrian rocks of Peun - 



sylvauia and Maryland, from the Sus- 

 qnelianua to the Potomac. 



Am. Journ. Sci., XLIV, 1892, pp. 469-482. 

 This paper is a continuation of the study of 

 the Cambrian locks of the Appalachian range 

 north of Virginia, between the Potomac and 

 the Susquehanna rivers. It records the dis- 

 covery of the Middle Cambrian fauna in a 

 series of quartzites that extend from Harpers 

 Ferry on the Potomac to South Mountain in 

 ; Pennsylvania, and which also occur in Tork 

 County, Pa., on the Susquehanna. It was also 

 discovered that a series of limestone shales 

 severa thousand feet in thickness belong to 

 the Lower Cambrian series. 



Report <m the Department of l*aleo- 



zoii- Fossils in the U. S. National 

 Museum, 1890. 



1 Hep. Smithsonian Inst. (U. S. Nat. Mus.), 



i 1890 (1891). pp. 233-234. 



WARD, Lester F. [Abstract of] The 

 plant-bearing dcpttsits of the American 

 Trias. 



Proc.Am. Assoc. J.(r«..S'ct., XLCWashington 

 meeting), 1891, pp. 287-288. 

 Abstract of paper of same title published in 

 Bull. Geol. Soc. Am., in, 1891, pp. 23-31. 



[Abstract of] Principles and methods 



of geologic correlation by means of 

 fossil plants. 



I Proc. Am. Assoc. Adv. Sci., XL (Wasliington 



meeting), 1891, pp. 288-289. 

 Abstract of paper of same title iu Am. Geolo- 

 gist, IX, 1892, pp. 34-17. 



[Abstract of] The science and art of 



Government. 



Proc. Am. Assoc. Ado. Sci., XL (Washing- 

 ton meeting), 1891, pp. 420-421. 

 A paper read iu abstract before Section I 

 (Economics and Statistics) of the American 

 Association for the Advancement of Science, at 

 its Washington meeting, iu August, 1891. Pub- 

 lished iu Science, xvni, November 20, 1891, p. 

 281. 



[Abstract of] A national university; 



its character and purpose. 



Proc. Am,. Assoc. Adv. Sci., XL (Washington 



meeting), 1891, pp. 421-422. 



A paper read in abstract before Section I 



(Economics and Statistics) of the American As 



sociation for tlie A«lvaucement of Science, at 



