1877. ] Pseudis, The Paradoxical Frog.” 587 
The uniformity of trend in glacial striz and drift transporta- 
tion observable over wide regions appears inconsistent, at first 
view, with the supposition that the ice-cap had but little erosive 
power: a contradiction seems implied in the possession by a 
glacier of a magnitude and rigidity which enabled it to move 
- without deviation over prominent reliefs, and a general inability 
to erode those reliefs. How can we harmonize the lightness of 
its tread with its rectilinear march over uneven surfaces? That 
ice in glacier masses behaves essentially as a very viscous liquid 
is well known; and a solution of the problem is found in a 
peculiar condition, pointed out by many writers, and necessarily 
existing in a continental glacier, which limits the freedom of 
motion among themselves, possessed by the different portions of 
the ice-sheet, to a vertical direction. Lateral deviation is ren- 
dered impossible by the inferior plasticity of the ice; and hence, 
when any portion of the ice-sheet encounters an obstacle, around 
which it would flow if sufficiently fluent, it is found easier to 
overcome the gravity of a small mass of ice than the cohesion of 
a relatively large mass, and the ice, moving in the direction of 
least resistance, passes in a vertical plane over the obstruction. 
j 
` 
PSEUDIS, “THE PARADOXICAL FROG.” 
O BY S. W. GARMAN, 
psEvDIs isa peculiar South American frog, peculiar in the 
fact that it grows smaller as it becomes adult, and in pos- | 
sessing a nearer approach to a thumb than any of its relatives. 
It is much to be doubted whether there is anything in the actual 
history of an individual belonging to this genus that calls for an 
amount of notoriety to which the most common toad or frog 
May not aspire. To be sure, the tail is kept long after all the 
legs appear; the tadpole is larger than the adult, and the creat- 
ure has a hand in which the thumb is opposed to the three fin- 
gers, yet all these are hardly enough to demand the amount of at- 
tention of a certain kind which the genus has received. In fact, 
as often happens in the case of men, Pseudis owes much of his 
_ Teputation to a mistaken estimate. Ifwe might trace him from 
as early a period as men have seen until well advanced in life, 
We should probably see nothing more than takes place in the his- 
tory of all batrachians. We might meet the egg first coming 
Within the limits of our vision as a round, granule-like body be- 
