TRANSACTIONS 



OF THE 



American Philosophical Society 



Held at Philadelphia, 



FOR PROMOTING USEFUL KNOWLEDGE. 



Vol. XX, New Series, ^to, pp. jp/, with g Plates. 

 Lately Published. 



CONTENTS. 



Art. I. — The History of the Pelycosauria, with a Descrip- 

 tion of the Genus Dimetrodon Cope. By G. 

 Ba-ur 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. 



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separate parts are not sold. 



Address THE LIBRARIAN OF THE 



American Philosophical Society, 



No. 104 South Fifth Street, 



Philadelphia, U. S. A. 



