476 E. N.S. Ringueberg—Dinicthys from New York. 
which would tend to increase precipitation at this line inde- 
saebnaeag of the relative humidity; so that if the relation 
etween relative humidity and precipitation is not simple an 
direct, it is probable that precipitation at the glacial isotherm 
increases more rapidly rather than less rapidly than the relative 
humidity. 
I must conclude therefore, as I did before, that ‘‘ the rate of 
decrease of temperature and the mean saturation will probably 
be greater in the warmer period . . . near the glacial isotherm, 
and indeed on the same grounds, for I prepared a passage for 
my former paper presenting in a more condensed form precisely 
the arguments here offered, but omitted it as being manifest 
without special mention. ; 
e argument here presented does not include all the impor- 
tant factors involved in the relations of temperature to glacia- 
tion, some of the others being sketched in my previous paper. 
at here offered, however, may serve to show the essential 
part which convection plays in the distribution of precipitation. 
San Francisco, Office U. 8S. Geological Survey, Feb., 1884. 
Art. LIX.—A New Dinicthys from the Portage Group of Western 
: New York; by Euarene N. §. RINGUEBERG. 
TAKING advantage of one of the pleasant days of January 
to make a short trip, down among the black carbonaceous 
shales of the Portage Group, to a fine exposure extending 
along the lake shore at Sturgeon Point, a projection of land 
about twenty miles below Buffalo, principally for the purpose - 
of obtaining some of the Calamites found there, I was so tor- 
tunate as to obtain, besides a quantity of undetermined fish 
scales, the fossil here described 
mmense placoderms of the genus Dinicthys have been 
known for quite a number of years past from the Huron shales 
of Ohio; but none till now have been recognized from Its 
equivalent in this State. | 
The specimen found consists of a dorsal shield belonging to 
a Dinicthys which exhibits such distinctive specific variations 
from the two Ohio species, D. Hertzeri and D. Terrelli Newb. 
both in size (which is only one-fifth of that of the largest of 
this species), and in form, as to require a specific description. 
_ Dinicthys minor (n. sp.) 
Dorso-median shield. Surface having a fine grained rugose 
appearance. Plate gently arched anteriorly and gradually 
: 5 toward the flattened posterior eatald which is but 
