CLIMATES OF GEOLOGIC TIME—-SCHUCHERT. 299 
Pompeckj, Buckman, and Smith state that late Triassic time was 
a particularly critical one for the ammonites. Of the far more than 
1,000 known species of Triassic ammonites, not one passed over into 
the Jurassic, and but a single family survived this time, the Phyl- 
loceratidee. Pompeckj says that “out of Phylloceras has developed 
the abundance of Jurassic-Cretaceous ammonites”? (1910), while 
Buckman holds it was out of Nannites by way of the Liassic Cymbites 
that the later fullness of ammonite development came. 
In the Liassic there are now known 415 species of insects that 
remind one much of modern forms. Nearly all were dwarf species, 
smaller than similar living insects of the same latitude and far 
smaller than Paleozoic or Upper Jurassic insects. Handlirsch (1910) 
is positive that this uniform dwarfing of the Liassic insects was due 
to a general reduction of the climate and that the temperature was 
then cool and like that of present northern Europe between latitudes 
46° and 55°. The climate, he states, was certainly cooler than either 
that of the Middle Triassic or Upper Jurassic. 
In this connection we must not overlook the fact that the known 
_ Liassic insects are of wide distribution, for 172 species are known 
from England, 164 from Mecklenburg, northern Germany, 75 from 
Switzerland, and 2 from upper Austria. With this depauperating of 
the insects and the vanishing of the late Triassic ammonites, there is 
also. to be noted a marked quantitative reduction and geographic 
restriction among the reef corals of Liassic time. We therefore are 
seemingly warranted in concluding that the cooling of the climate in 
late Triassic and early Jurassic time was not local in character, but 
was rather of a general nature. Much workable coal was also laid 
down in Liassic time, not only in Hungary but also im many places east- 
ward into China and Japan. In addition, the many black shales of 
this time furnished further evidence of cool and nontropical climates; 
coal and black shales are so general in occurrence throughout the 
Liassie rocks that the time is often referred to as the Black Jura. 
Finally, certain Liassic conglomerates of Scotland have been thought 
by some to be of glacial origin. (J. Geikie.) 
Jurassic.—The Jurassic formations of Europe are so rich in fossils 
that they have been the classic ground on which many paleontologists 
and stratigraphers were reared. From the studies of these faunas 
came the first clear ideas of climatic zones and world paleogeographic 
maps through the work of the great Neumayr of Vienna. As the result 
of a very long study of the ammonites and their geographic distribu- 
tion, he came to the conclusion in 1883 that the earth in Jurassic time 
had clearly marked equatorial, temperate, and cool polar climates, 
agreeing in the main with the present occurrence of the same zones. 
He also said that ‘‘the equator and poles could not have very much 
altered their present position since Jurassic times.” His conclusions 
