664 THE AMERICAN NATURALIST. (VOL XXXII. 
due to differences of climate, a view reiterated by Kayser 
(p. 283). Scott also states that the Lower Cretaceous beds of 
Texas show faunal resemblances which ally them to the Portu- 
gal and Mediterranean beds, while the faunal relations of South 
American Lower Cretaceous strata are closely like those of 
northern and western Africa. 
The biological changes at the beginning of the Upper Cre- 
taceous were correspondingly notable. Vast forests of conifers, 
palms, and especially of deciduous trees, such as the oak, sassa- 
fras, poplar, willow, maple, elm, beech, chestnut, and many 
others, clothed the uplands, while in the jungles, on the plains, 
and in the openings of the forests, gay flowers bloomed. The 
flora must even then have been, comparatively speaking, one 
of long existence, because highly differentiated composite 
plants, like the sunflower, occur in the Upper Cretaceous or 
Raritan clays of the New Jersey coast. It may be imagined 
that with this great advance in the vegetables, the higher 
flower-visiting insects must have correspondingly dain cee in 
number and variety. 
While the changes of level did not affect the uiia of the 
sea, the topography of the shallows and coast was materially 
modified, and to this was perhaps largely due the extinction of 
the ammonites and their allies.! It is not impossible that the 
1 After preparing this address, I find that Wood thirty-six years ago more fully 
discussed this matter, and mentions the same cause we have suggested. ‘This 
disappearance,” he says, “of the Ammonitidz, and preservation of the N autilide, 
we may infer was due to the entire change which took place in the condition of 
the shores at the close of the Cretaceous period; and this change was so complete 
that such the shore followers as were unable to adapt themselves to it suc- 
cumbed, while the others vey aiea themselves to the change altered their 
specific Persiaa altoget e Nautilidæ having come into existence long 
prior to the introduction of a Ammonitide, and having also survived the eee 
tion of the latter family, must have possessed in a remarkable degree a pow 
adapting themselves to altered conditions.” On the other hand, the dibranchiate 
cephalopods (cuttles or squids), living in deeper water, being “ ocean-rangers,” 
were quite independent of such geographical PESTE Wood then goes on to 
_ say that the Pea es of the tetrabranchiate group affords a clew to that of 
the Mesozoic saurians, and also of cestraciont hth whose food probably con- 
sisted mainly of the tetrabranchiate cephalopods. “Now the disappearance of 
the Tetrabranchiata, of the cestracionts, and of the marine saurians, was contem- 
poraneous ; and we can hardly refuse to admit that such a triple destruction must 
have arisen either from some common cause or from these forms being succes- 
