80 
uniquely specialized forms slowly disappear towards Tertiary 
time, to recur no more. With them, too, go the Araucarias, 
save that these still persist in South America. 
It is possibly an over-emphasis of evidence to call attention 
to such general facts. It is probable, however, that for Cre- 
taceous time, the period of driest intra-continental climates is 
marked by the culmination of the cycadeoids ; and it is moreover 
unlikely that a single species so far recovered lived far from the 
border of open and dry country. No other fossil plants are 
more obviously xerophyllous. Though reference is made solely 
to the large-stemmed forms with a great pith and thin woody 
cylinder; it should be emphasized that many of the relatives, 
both near and distant, must have had the capacity to live in 
every zone and climate. 
It is desirable to add that the exact position of the Trinity 
beds is only in a general way indicated as equivalent to the lower 
Potomac by the cycad found by Dr. Bose. But the specimen 
is so like the Potomac forms that it could be a constituent of one 
and the same forest. Dr. Bose says it came from the base of 
the Wise County Cretaceous sandstones as they transgress the 
Pennsylvanian. But he adds that this is scarcely the lowermost 
Cretaceous in the European sense, being rather an equivalent of 
the Aptien, or uppermost part of a true Lower Cretaceous. His 
views on the position of the Trinity are more fully given in a 
monograph on the Cerro de Muleros brought out by the Institute 
Geologico of Mexico, and a satisfactory notice with tabulation 
may be found in Willis' “Stratigraphy of North America” (page 
588 et seq.). 
Some further facts of interest here are found in an earlier 
paper of Fontaine 1 , who describes some twenty-three species of 
fragmentary leaves and twigs from the bed of Paluxy river, 2 
miles above Glen Rose, Texas, or only 60 miles south of the 
point in Wise county which yielded the petrified stem (accom- 
panied by petrified forests). These plants are found in a grey 
1 Notes “on some fossil plants from the Trinity beds of the Comanche 
series of Texas,” Proc. U.S. Nat. Mus., vol. XVI, 1893, pp. 261—282, plates 
XXXVI-XLIII. 
