50 The American Naturalist. [January, 
GEOLOGY AND PALEONTOLOGY. 
A Food Habit of the Plesiosaurs.—Mr.S. W Williston re- 
ports finding a number of pebbles in such a position with respect to 
the bones of a Plesiosaur discovered in the Niobrara chalk in Kansas 
that the conclusion is irresistible that the stones had been in the stom- 
ach of the reptile. They had probably been swallowed to aid in diges- 
tion, a custom still in vogue among the Crocodiles. Some of the 
pebbles were attached by the original soft limestone matrix to the ribs 
and thoracic vertebri, so that there could not be a shadow of a doubt 
as to the contemporaneity of deposition. ` 
The saurian is one of the largest of the order, measuring when alive 
about fifty feet. The pebbles, 125 in number, are extremely hard, con.. 
sisting almost wholly of silica, varying in weight from 1 to 170 
grams. They are conspicuous in color, either white, black or pink, 
and show a great amount of abrasion, and probably came from the 
shores of the Benton sea. 
From the uniformity of shape among the smaller ones, their number, 
and their color, Mr. Williston is inclined to think they were not 
merely water-worn pebbles, accidentally swallowed, but they had been 
selected by the saurian for a purpose, and that their present shape is 
owing to their prolonged use as “ gizzard stones” in the animal’s 
stomach. (Trans. Kansas Acad. Sci., Vol. XIII, 1891-92.) 
The Texas Region.—In a recent paper on the physical geography 
of Texas, R. S. Tarr embodies the results of his personal observation 
with the published geological work of others in the same region and 
summarizes the geological history of Texas as follows: 
“The evolution of the Texas region began with an old Paleozoic or 
Pre-Paleozoic mountainous land which was denuded at the beginning 
of Carboniferous times to an old topographic form, not unlike the hilly 
region of southern New England. The Carboniferous beds were added 
to this land, by elevation, first as a costal strip, even before the end of 
the Carboniferous. A gathering in of shore lines formed a great in- 
terior sea, later a completely land-locked dead sea in which Permian 
beds were deposited; and from the close of the Permian to the begin- 
ning of the Cretaceous there was a period of denudation during which 
the younger Paleozoic beds were reduced to base-level and the older 
mountainous areas still farther degraded. A rapid subsidence lowered 
Wee tae ea ee eee eee a 
