102 ROYAL SOCIETY OF CANADA! 
them to be of Jackson age.” And further, he points out (op. cit. 108) 
that “With the exception of the lignite and characteristic Jackson 
fossils, the description given by Hopkins would answer for the Texas 
Frio clays as well as for the Yegua clays”; and he considers that 
“The usual interpretation of the work done in Louisiana can hardly 
be accepted, and until information is obtainable, the correlation of the 
beds in these states must be left an unsolved problem” (op. cit. 108). 
His own conclusions, nevertheless, point directly to the adoption of a 
definite correlation of the Yegua clays with the Lower Claiborne of the 
Mississippi section (op. cit. 92). 
Finally we come to the conclusions of Harris (5, 45) based upon 
a study of the molluscan fauna, in which he says that “The Lower 
Claiborne beds are replete with fossils, many of which are common to 
this horizon in Louisiana, Mississippi, Alabama and South Carolina,” 
but “The true Claiborne, the Jackson and Vicksburg stages, seem to 
have no representation in Texas. This fact cannot be too strongly 
emphasized since most writers on Texas geology have referred certain 
fossil bearing outcrops to some of these Upper Eocene stages.” In 
discussing the distribution of the fossils described, he definitely refers 
to the Yegua clays as of Lower Claiborne age. 
With respect to the chemical nature of the Yegua clays and their 
possible origin, Kennedy (9, 298, 299) points out that their contained 
water is strongly saline and that potash is present to the extent of 1.07 
per cent, and soda 2.33 per cent. Furthermore, the basal beds of the 
Tertiary bear a very strong resemblance to the underlying contiguous 
beds of the Cretaceous, and “ In lithological as well as chemical struc- 
ture, it is very difficult to tell them apart, and in many portions nothing 
but a study of the fauna will enable anyone to differentiate the two; 
in many places the Tertiary beds contain boulders and fragments of 
Cretaceous limestones containing Cretaceous fossils.” He therefore 
concludes that “It would thus appear that the structural conditions of 
the Basal beds and the Fayette deposits, apart from any chemical evi- 
dence whatever, bears out the assumption of these two divisions being 
derived from the Cretaceous.” 
Whether the Yegua clays were derived from the Marine beds 
through their erosion and consequent destruction, is not very clear, but 
“The presence of extensive deposits of lignites in these beds would 
appear to indicate another source of material having a swamp or lagoon 
origin, and some of it may have been obtained from the rivers travers- 
ing the region. Some of the materials employed in the formation of 
these beds may also have been derived from the sea water occupying 
the area during the period of deposition.” (op. cit. 300). 
