X CONTENTS. 



ARTICLE X. 



Page 



On the decomposing power of Water at High Temperatures. By Richard A. Tilghman, . 173 



ARTICLE XL 

 On the Neutral Sulphate of the Oxide of Ethyle, and the products of its decomposition by water. By 



Charles M. Wetherill, Doctor of Philosophy, 177 



ARTICLE XII. 



De Calculo Eclipsium Bcsseliano Commentatio. Auctore Dr. Gustavo Adolpho Jahn. Lipsioo, 1848, . 183 



ARTICLE XIII. 

 On the Longitude of Washington, computed from the moon-culminations observed during the Years 1839 



— 1842, inclusive. By Lieut. J. M. Gilliss, 211 



ARTICLE XIV. 



On the Accuracy of the Tabular Longitude of the Moon, to be obtained by the construction of New Lunar 



Tables. By Miers Fisher Longstreth, 225 



ARTICLE XV. 



On the Organization of the Genus Gregarina of Dufour. By Joseph Leidy, M. D., .... 233 



ARTICLE XVI. 



Some Observations on Nematoidea Imperfecta, and descriptions of three Parasitic Infusoria}. By Joseph 



Leidy, M. D., 241 



ARTICLE XVII. 



Meteorological Observations, Napa-Keang, (Loo-Choo,) 1848 — 1849. Made by Dr. Bcttclheim, . . 245 



ARTICLE XVIII. 



Descriptions of New Species of the Family Unionidce. By Isaac Lea, ....... 253 



ARTICLE XIX. 



Description of a New Genus (Basistoma) of the Family Melaniana, together with some New Species of 



American Mclania;. By Isaac Lea, ............ 295 



ARTICLE XX. 



Description of a New Species of Helix, from California, and a new Characteristic Form of certain American 



Colimaceae. By Isaac Lea, 303 



ARTICLE XXL 



On the Fossil Foot-Marks in the Red Sandstones of Pottsville, Schuylkill County, Pennsylvania. By 



[saao Lea, ....... ........ 307 



ARTICLE XXII. 



Description of an extinct species of American Lion : Feus Atrox. By Joseph Leidy, M. D., . 319 



ARTICLE XXIK. 

 A Memoir on the extinct Diootylinsa of America. By Joseph Leidy, M. D., . 323 



