


446 PROCEEDINGS: OF SCIENTIFIC SOCIETIES. 
continued pressure and tension probably at a moderate elevation of tem- 
perature (but not necessarily so) had been sufficient to produce the mole- 
cular movement of these hard and apparently unyielding materials. 
Mechanical force alone appeared to have been the agent, and M. Tresca 
had shown that under enormous pressure solids could be made to flow in 
the same manner as liquids, or that in their movements they followed the 
same law. By the careful study of these phenomena of plasticity new 
views were opened of the structure of great rock masses; of the pheno- 
mena of plication, lamination; and of the origin of some structural pecu- 
liarities of mineral veins and their enclosing walls. In view of all the 
mechanical pressure, unaided by any great elevation of temperature or by 
extraordinary chemical agencies. 
C. Marsu read a paper ‘on some new Mosasauroid Reptiles 
e n 
appeared to have no hind limbs, although Cuvier thought he had detected 
them. The specimens found in this country, however, afforded no evi- 
[e] 
oO 
© 
See 
The larger specimens of these animals showed that they must hav l 
the monarchs of the seas of those periods, and in appearance and size not 
unlike the popular notion of the sea serpent, being sometimes seventy- 
five feet long. 
** On the Flora and Fauna of the Miocene Tertiary Beds of Oregon and 
Idaho." Prof. Newberry exhibited a beautiful series of fossil plants col- 
lected by Rev. Mr. Condon of Dallas City, Oregon. These plants were 
_ from the fresh-water deposits which cover so large a surface of the Great 
_ Basin in Nevada, Idaho and Oregon, and were of special interest both 
Mt from their geological position and botanical character. They were con- 
. tained in the sediments deposited by a series of great fresh-water lakes, 
. Which once existed in the area lying between the Rocky Mountains and 
Sierra Nevada. - jogs 



