214 H. H. Howorth—The Fauna and Flora of the Loess. 
they will have it the Loess is a lacustrine deposit, and Mr. Elsworth 
Call tells me that the American authorities upon the Loess, including 
himself, Dana, Packard, Powell, Hayden, McGee, Russell, Dutton, 
White, etc., all maintain the same view. I cannot concur in this 
lacustrine theory, at least as applied to Europe and China, but 
I do hold strenuously with them that a large portion of the 
shells found in the Rhine Loess necessitate a humid condition 
of things. No doubt some of the Molluscs point to upland dis- 
tricts and to drier conditions, but these are quite a minority. M. 
Daubrée, who reported on 200,000 specimens from the Rhine Loess, 
says, ‘‘ Nearly all still live in cold damp climates, and some in the 
Alps as high as the limits of snow.” Heer says of the shells 
from the Upper Rhine Valley, all the species except Helix ruderata, 
Hi. sericea, H. glabella, H. arbustorum, H. subalpina, which belong to 
mountain districts, and Helix strigella, with a wide umbilicus, which 
is locally limited, are either forest-snails from the region of leafy 
trees, or species which prefer shady moist places, inhabitants of 
many localities are wanting. M. Tournouér, a first-rate authority, 
speaking of the similar Molluscs from the Seine Valley, says, ‘‘They 
must have lived in the recesses of moist woods attached to leaves, to 
tender herbaceous plants, and to rocks where waters fell. ..... 
They bespeak a diffusion of European species more uniform than 
prevails now, with a damp and more uniform climate than now 
prevails.” But we need not surely enlarge on this part of the 
subject. Any one who will take the trouble to sift out the propor- 
tion of Succineas found in the Rhine Loess, and who is aware of the 
life conditions of this most common Mollusc, will assuredly never 
assign as its habitat in the Mammoth period dry Steppes continually 
blown over by fierce winds. I do not dispute that the upland tracts 
which we know existed in Germany in Post-Glacial times, and were 
characterized by their own fauna, were also the home of a certain 
number of Helices, etc., which frequent mountain slopes. This is 
perfectly certain, but it does not in any way affect the problem as 
I stated it, nor does it mean the importation into Europe of the 
parched conditions that prevail in Mongolia, where the ground is 
practically bare, and where Pumpelly could say that in travelling 
from Kalgan to Urga, a distance of 420 miles, he only saw two trees. © 
I have now done. I have frankly faced every argument produced 
by Dr. Nehring. I do not profess to contest the brilliant series of 
facts he has so carefully collected, but I do claim to have shown 
that these facts and the inferences they necessitate are completely 
fatal to Baron Richthofen’s theory. In conclusion, I would add 
that even if they had not been so, they surely affect one element and 
factor in the problem, as he states it only, namely, the biological 
element, and the various objections, geological and otherwise, adduced 
by myself and others, remain unanswered. I hope some effort at 
all events will be made to meet them, for we are all engaged in 
hammering iron, and the only product of our labours which is likely 
to live is that which has been well hammered on every side. I hope 
also that Dr. Nehring will find nothing in tone or substance in this 
