136 BULLETIN: MUSEUM OF COMPARATIVE. ZOOLOGY. 
further noted by Kurtz, who has found in certain beds exposed in 
the Argentine Republic a number of fossils which show them to be 
allied to the lower Gondwana rocks of India (Kurtz, p. 111 et seq.). 
Crush-Conglomerates. “Where rocks lie under too light a load to 
become plastic, and have, therefore, given way to great crushing by 
breaking to pieces, their broken fragments may be pushed along shear 
planes or in fault zones, and may thus be pressed against each other 
and rolled forward, until their edges are rounded off and they acquire 
much resemblance in general form to the pebbles of a conglomerate. 
Bands of such comminuted materials are of not infrequent occurrence 
among Palaeozoic and older formations which have suffered much 
disturbance. They are known as Crush-conglomerates, or, when 
the fragments are angular, as Crush-breccias” (A. Geikie, p. 683). 
Rocks of this character in the Isle of Man are described by Lamplugh, 
who notes the gradual smashing into fragments of highly contorted 
strata until every trace of the original bedding is lost and a crush- 
conglomerate with lenticular and partly rounded inclusions is formed 
(Lamplugh, p. 372-373). A similar instance in Argyllshire is described 
by J. B. Hill. Limestones with epidiorite sills have been intensely 
folded and isoclined (J. B. Hill, p. 313 et seq.). The epidiorite has 
been fractured and in some instances rounded so that the appearance 
is that of boulders in a limestone matrix. Fragments of the epidio- 
rite (ibid., p.g3824) may be seen here and there enclosed in the main 
mass, as well as the remains of crests and limbs of folds that have been 
torn from their original position and formed into augen-structures. 
Combinations of Processes. It is evident that conglomerates may 
be formed as the result of the action of two or more of the processes 
already mentioned. For example, the glacial deposits which are so 
abundant in New England are in many places being worked over by 
the sea. The angular and subangular striated pebbles of the till are 
being rounded and sorted by wave action in many places along the 
present beaches. The mill of the sea quickly removes the glacial 
markings and the rounded pebbles soon produced cannot in them- 
selves be distinguished from those formed by marine action alone. 
It is only when the modified deposits can be seen in proximity to 
unmodified portions of the mass from which they were derived that 
their originally glacial character can be assumed with confidence. 
In the Champlain valley extensive lakes, dammed by the retreating 
ice sheet, and the later invasion of the sea itself have produced a number 
of shore lines at different levels, which have recently been described 
in some detail by Professor Woodworth. Beaches have been formed 
