TRANSACTIONS 



OF THE 



American Philosophical Society 



Held at Philadelphia, 

 FOR Promoting Useful Knowledge. 



/ 'ol. XX, Nezv Series. Pai^t /, ^to, pp. 62, with j Plates. 

 Lately Published. 



CONTENTS. 



Art. I. — The 11 i story of the Pel5^cosauria, with a Descrip- 

 tion of the Genus. Dimetrodon Cope. By G. 

 Baur and E. C. Case. 



Part II. ^lo, pp. 7/^, with 5 Plates. 

 Just Published. 



CONTENTS. 



Art. II. — The Chronolog-ical Distribution of the Elasmo- 

 branchs. By O. P. Hay. 



An. 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. Montgomerv, Jr., 

 Ph.D. 



SUBSCRIPTION— FIVE DOLLARS PER VOLUME. 



SLPAkATB PARTS ARB NOT SOLD. 



A.ki;ess THE LIBlfARlAN OF THE 



American Philosophical Society, 

 No. 104 South Fifth Street, 



Philadelphia, U. S A. 



