Correspondence, 121 
long interglacial period, as urged by McGee"^ is not pertinent. Certain 
it is, however, that the remarkable abundance and wide geographic 
distribution of many of the loess shells is indicative of a considerable 
period, after the recession of the glacier, during which the climate 
must have been comparatively mild in order that the numerous spec- 
ies of land mollusks could reach such an immense development, and 
attain such a wide dispersion as is clearly manifest. That the climatic 
conditions, however, were much more rigorous than at present is am- 
ply shown not only by a notable depauperation of ttie moUu.scan shells 
as first i)ointed out by McGee and Call,' but it is also attested by the 
introduction of many boreal forms, some of which have been already 
enumerated. The presence, during the deposition of the loess, of arc- 
tic species in Iowa is further evidenced by the discovery of the re- 
mains of such northern mammals as Ovibos cavifrons,^ and Cervus mu8- 
The driftless area — formerly a veritable Jardin midst a vast waste of 
ice — is therefore of peculiar interest in considering geographically the 
faunal distribution during a time when the climatic conditions of the 
region were manifestly very dilTerent from those of the present, and it 
is not improbable that within the limits of the tract mentioned careful 
search among the moUusca and plants will yet reveal many significant 
traces of boreal life — vestiges of an arctic season. 
Burlington, Iowa. Charles R. Keyes. 
The T.\con'Ic of Eastern Newfoundland.— Through the kind permis- 
sion of professor ^larcou and the author, Mr. James P. Howley, geolo- 
gist of St. John, Newfoundland, we are enable to place the following 
interesting letter before the readers of the Geologist. 
St. Johns, Neufotindlatid, April 24th, 1SS9. 
Professor Jules Marcou. 
Dear Sir. — I have read with the greatest interest your pamphlet on 
"Canadian Geological Classification." Although I am but a field 
geologist and have neither time nor opportunity for indulgence in theo- 
rizing, I can appreciate your work, the more esjiecially since many of 
your ideas coincide exactly with what I have always l)elieved. For in- 
stance, I never could see the sense of representing faults to account 
for ajiparent incongruity where no fault was visible, or no facts to sus- 
tain such rejiresentation. On this head, and indeed on many others 
concerning which we difTered, Mr. Murray and I had frequent discus- 
sions. Being a subordinate I was often obliged to give way, but in one 
or two notable instances where I had clear, indisputable evidence to 
bring forward, he gave way to me. 
On our west coast the Carboniferous series of Newfoundland rests on 
•Top. Sci. Mo., Nov. 1888, p. 26. 
'Am. Jour. Sci., Si'j)!. 1SS2, vol, x.\iv. 
^McGee: Am. Jour. Sci., (.3), vol. x.wiv, p. 217. 
*Leidy: Proc. Acad. Nat. Sci., Phila., xxxi, p. 32. 
