W. IT. Dall — Pliocene Conditions at Nome. Alaska. 457 



Art. XLY. — On Climatic Conditions at Nome, Alaska, dur- 

 ing the Pliocene, and on a new Species of Pecten from 

 the Nome Gold-hearing Gravels', by William ' Healey 

 Dall,* Paleontologist IT. S. Geol. Survey. 



The conditions indicated by the faunas of the Post-Eocene 

 Tertiary on the Pacific Coast from Oregon northward are a 

 cool temperate climate in the early and middle Miocene, a 

 warming up toward the end of the Miocene culminating in 

 a decidedly more warm-water fauna in the Pliocene, and a re- 

 turn to cold if not practically Arctic temperatures in the Pleis- 

 tocene. In these particulars the climatic variations are not 

 unlike those of the southeastern Atlantic Coast of the United 

 States. 



On the north side of Norton Sound, Alaska, where the town 

 of Nome is situated, the conditions are practically Arctic at the 

 present time, as the sound is covered with heavy ice during a 

 third of the year or even more. 



This gives a particular interest to a small collection of marine 

 shells from the gravels near Nome, recently received through 

 Dr. A. H. Brooks, U. S. G. S., from Messrs. Moffit and Beaver 

 of Nome. 



These prove to contain, not only species inhabiting at present 

 only a more southern habitat, but also a conspicuous large 

 scallop at present living only in northern Japan, the Pecten 

 swifti Bernhardi, a most unexpected find. 



Several species occur, like Monia macroschisma Desh., and 

 Macoma middendo?'ffi Dall, which are now known in the living 

 state only south of the line of floating ice in winter, in Bering 

 Sea and the Aleutian Islands. 



Nine determinable species were found, of which four extend 

 from the Arctic to Puget Sound at the present time ; three are 

 known only from south of the winter line of floating ice ; one 

 occurs at Hakodacli, Japan, and the following, probably extinct 

 species, appears to be new. 



Under the circumstances the gravels in question are identi- 

 fiable as Pliocene in age, but that there are both later and 

 earlier gravels on the northern coast of Norton Sound is quite 

 probable. 



Pecten ( Chlamys) lioicus Dall, n. sp. 



Shell of the general form of P. islandicus Miiller, but ex- 

 ternally smooth, or sculptured only with incremental lines and, 

 near the posterior basal margin, with extremely faint indica- 

 * By permission of the Director of the U. S. Geological Survey. 



