Termination of the Paleozoic Period, §c. 365 
gravity. It is evident that what applies to these substances can- 
not be advanced as a general rule. 
Niobie acid has a far lower specific gravity than pelopic acid. 
It exhibits a similar behavior. The acid, exposed to the temper- 
ature of the porcelain furnace, appears under the microscope per- 
fectly crystalline. 
antalic acid behaves very different from the other two acids. 
It is the heaviest of all, and, by heating to redness in a charcoal 
fire, increases considerably in specific gravity, from 7-0 or 7:1 to 
8-2. In the fire of the porcelain furnace it is likewise converted 
into a coarse powder, but which does not appear distinctly crys- 
talline under the microscope. Its specific gravity is thereby only 
slightly lessened. 
nall these experiments no alteration in the absolute weight 
was perceptible. . 
Arr. XXXVII.— Termination of the Paleozoic Period, and 
Commencement of the Mesozoic; by D. D. Owen, M. D. 
~ 
Some of the most distinguished and experienced geologists 
seem, from their recent publications, disposed to include the Per- 
mian system, in the Paleozoic division of the fossiliferous strata, 
regarding it as the terminating group of that period. "Their argu- 
ments in support of this view, are— ) f 
The corals of this system are considered to have a palwozoic 
Sei dey 3 ed 
* The tables only show nine species. 
beak be table ae Pocrtalle aidan (Gorgonia antiqua, Goldf.) as common to 
¢ Permian, Devonian and Silurian systems; and Fenestella dubia. 
+See note Sur les equivalents du system Permien, par M. de Verneuil, p. 8. 
