1885. | Geology and Paleontology. I21I 
sygnatha only a single pair of legs is borne by each segment, 
and the group thus resembles the Chilopoda. For a brief period 
after leaving the egg, modern diplopods and pauropods have a 
shorter body than in after life, and the first three segments bear 
but a single pair of legs. In adult life these first three segments 
still bear but a single pair of limbs, while all the other segments, 
both those which exist in the larval state and those which develop 
afterwards, bear two pairs. The Chilopoda have these same three 
anterior pairs of limbs eariy and permanently developed as 
organs of manducation, while all other segments have but a sin- 
gle pair. Paleontological evidence is in favor of the view that 
the dorsal scutes of Diplopoda are compound. The archipolypo- 
dous type is the oldest, and there is evidence that some of the 
Carboniferous forms were amphibious. The group culminated in the 
Carboniferous, and does not appear, to occur later than the Dyas, 
while, with one doubtful exception, no true diplopod is known to 
be older than the Oligocene. According to S. H. Scudder be- 
tween twenty and thirty species of pre-Tertiary Arachnida are 
now known, and the earlier forms, chiefly of Carboniferous age, 
belong either to the scorpionides or to the Anthracomarti, a 
group which is not known later than Paleozoic times, the only 
Mesozoic arachnids yet known being true spiders. In the amber 
deposits of Prussia all the suborders of Arachnida occur except 
the Pedipalpi and the already extinct Anthracomarti. rG 
B. Villa (Atti. d. Soc. di Sci. Nat.) gives a review of the rocks of 
Brianza (Italy) with a list of the principal fossils of each horizon 
rom the Trias to the most recent strata. 
Mesozoic. —Bulletin No. 19 of. the U. S. Geological Survey 
consists of notes on the stratigraphy of California, by G. F. 
Becker. The metamorphic rocks of the coast ranges often show 
' proof that plication was not effected by flexure but by innumer- 
afterwards re-cemented by silica. The Knoxville beds, the age 
of which is near the limits of the Jurassic and Cretaceous, are 
the youngest beds of the coast ranges which are known to have 
experienced the peculiar magnesian and siliceous metamorphism 
of these ranges. The overlying Chico beds are shown to be non- 
conformable with the Knoxville beds, and over wide areas the 
Chico, Tejon and Miocene strata seem to be perfectly conforma- 
ble with each other. The upheaval and metamorphosis of the 
Knoxville strata is referred to the close of the period of their 
deposition. The auriferous beds of Mariposa are referred to the 
same horizon as the Knoxville beds. It is maintained that there 
has been a great east and west compression of the country, con- 
nected with the great faults in the Wasatch and the Sierra, while 
a land barrier existed in the position of the Sierras from a time 
prior to the Cretaceous onward, and accounts for the difference 
