Review of Recent Geological Literature. 335 
but now proved by David White, on the evidence of a large collection of 
plants, to be Middle Cretaceous. 
Prof. Ward next discusses the influence of geographical distance in 
lessening the identity of species in floras while the general aspect of re- 
semblance continues. Contemporaneity of date may be inferred from 
identity of species, especially in the more recent and not geographically 
remote strata: yet as we recede to a greater distance the forms are ex- 
tinct and their exact relationship isdifficultof determination, especially 
among the cryptogams. Hence more stress must be laid on close alli- 
ance than on identity, because the latter is frequently a matter of 
opinion of the palaeontologist. The essay is a valuable contribution to 
exactness in this department of geology. e. w. c. 
Fossil Plants as an aid to Geology. By F. H. Knowltox. Journal of 
Geology, vol. n, pp. 365-382; May -June, 1894. Prof. Knowlton takes up 
the same points as the foregoing paper and quotes largely from it regard- 
ing the use of plant fossils in the widest sense. As to their value in a 
more restricted area, he cites the remarkable case of the Dakota group 
which has yielded 460 species of plants, with only ten invertebrate and 
no vertebrate fossils. Of the plants 394 species are peculiar to that hor- 
izon, and many of these are so characteristic as to settle any question 
of the age of other beds in which they occur. As an instance of this, 
the author quotes the mistaken reference of a so-called specimen of 
Sterculia drakeii from the. Big Tucumcari beds of New Mexico as the 
only known dicotyledon from the Trinity sands of the Comanche series. 
It is, he says. Sterculia snowti of the Dakota group and at once deter- 
mines the age of the stratum in which it is found. Several other in- 
stances are given of the importance of plants in determining the age of 
Cretaceous strata in the west, such as the Colorado and Middle Park or 
Denver beds, the Livingston beds, and the Great Falls beds in Montana. 
Economically, Prof. Knowlton shows the value of palaeobotanj in quot- 
ing the case in which Zeiller predicted the discovery of a bed of coal in 
France on palaeobotanical grounds. A shaft was sunk, and at the depth 
of nearly 'I. 10" feet coal was found, having a thickness of aboul Bftecn 
feet. 
In writing of fossil plants as a test of climate, the author says, "the 
absence of rings of growth in the Carboniferous conifers shows, as long 
ago pointed out by William, that the seasons, if such they could have 
been called, were either absent or not abrupt.' - With this view it is 
not quite easy to coincide, because, not to discuss here the somewhat 
doubtful case of conifers, there were undoubtedly other Carboniferous 
plants whose remains exhibit (list in el rings of growth. 
In conclusion the author justly remonstrates against the too frequent 
pracl ice of expecting the palteobotanisl to determine mere fragments of 
plants uncritically collected and ill preserved. As well might a botan- 
ist be called on to name scraps of living plants badlj dried and sundered 
from each other. In both cases the task is often impossible or the re- 
sult is useless. K. W. C. 
'/'//( Post-Pliocent Diastrophism of tin Coast of southern California. \'<\ 
