TRANSACTIONS 
OF THE 
American Philosophical Society, 
HELD AT PHILADELPHIA, 
FOR PROMOTING USEFUL KNOWLEDGE. 
Vol. XX, New Series. gto, Dp. 397, with 9 Flates. 
Fust Published. , 
CONTENTS. 
Art. JI.—The History of the Pelycosauria, with a Descrip- 
tion of the Genus Dimetrodon Cope. By G. 
Baur and E. C. Case. 
Art. II.—The Chronological Distribution of the es 
branehs.;.By\O. RP) Hayy 
Art. III.—Results of Observation with the Zenith Telescope 
of the Sayre Observatory from January 19, 1894, 
to August 19, 1895. By CHaries L. Doo.iTTLe. 
Art. IV.—A Study of the Chromosomes of the Germ Cells 
of Metazoa. By THomas H. Monrtcomery, Jr., 
Ph.D. 
Art. V.—Fossil Mammalia of the White River Beds of 
Montana. By Eart Douc.ass. 
Art. VI.—Results of Observation with the Zenith Telescope 
of the Sayre Observatory from April 1, 1876, to 
December 27, 1893. By Cuartes L. DoouittLe. 
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