TRANSACTIONS 



OF THE 



American Philosophical Society 



Held at Philadelphia, 



FOR PROMOTING USEFUL KNOWLEDGE. 



Vol. XX, New Series. 4(0, pp. ^^gy^with g Plates. 

 Just Published. 



CONTENTS. 



Art. I. — 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 Elasmo- 

 branchs. By O. P. Hay. 



Art. III. — Results of Observation with the Zenith Telescope 

 of the Sayre Observatory from January 19, 1894, 

 to August 19, 1895. By Charles L. Doolittle. 



Art. IV.— A Study of the Chromosomes of the Germ Cells 

 of Metazoa. By Thomas H. Montgomery, Jr., 

 Ph.D. 



Art. V. — Fossil Mammalia of the White River Beds of 

 Montana. , By Earl Douglass. 



Art. VI. — Results of Observation with the Zenith Telescope 

 of the Sayre Observatory from April i, 1876, to 

 December 27, 1893. By Charles L. Doolittle. 



SUBSCRIPTION— FIVE DOLLARS PER VOLUME. 



separate parts are not sold. 



Address THE LIBRARIAN OF THE 



American Philosophical Society, 



No. 104 South Fifth Street, 



Philadelphia, U. S. A. 



