834 The American Naturalist. [September, 
WINCHELL, N. H—The Geological and Natural History Survey of Minnesota, 
Twenty-second Annual Report, for the year 1893. Minneapolis, 1894. 
——Annual Report for 1894, Minn. Geol. and Nat. Hist. Surv. Minneapolis, 
1895. From N. H. Winchell. 
Woopwarp, A. S.—Notes on Shark’s Teeth from British Cretaceous Forma- 
tions. Reprint Proceeds. Geol. Ass., Vol. XIII, 1894. From the author. 
——On a Second Species of Eurycormus. Extr. Geol. Mag., May, 1894. 
From the author. 
— On some Fish remains of the Genera Portheus and ee from the 
Rolling Downs Formation (Lower Cretaceous) of Queensland. e Affini- 
ties of the Cretaceous Fish, Protosphyraena.—— Extrs. Ann. Mag. Nat. ries Vol. 
XIII, 1894. From the author. 
General Notes. 
MINERALOGY.’ 
Universal Stage for the Microscope.—Federow has done a 
great service to mineralogists and petrographers by introducing instru- 
ments based on the universal or theodolite principies. His application 
of these principles to the measurement of crystal angles is the gonio- 
meter with two graduated circles, which has already been referred to in 
these notes. Extending his study to the field of crystallographic- 
optical measurements, he has devised the universal microscope stage,’ 
which increases the usefulness of the microscope by permitting a quite 
new class of observations to be made. The microscope stage now in 
use permits of only such motions as always retain the slide in a plane 
parallel to the initial one. Federow’s universal stage allows the slide 
to be moved into any position whatsoever by two rotations about axes 
normal alike to one another and to the microscopés axis, He has 
described and figured two different types of stage, one better adapted 
to ordinary work and also permitting the slide to be immersed in liq- 
uids if desired, while the other has the advantage of greater simplicity 
and has a convenient arrangement for orienting the slide in its own 
plane, so that any line (e. g., a twinning trace) may be brought parallel 
to the immovable axis of the stage. In answer to some inquiries, 
1Edited by Dr. Wm. H. Hobbs, University of Wisconsin, Madison, Wis. 
_ ? Zeitsch. f. Kryst., xxii, pp. 229-268, pl. 9 (1893). 
