CONTENTS. 



Art. VII. — The Cretaceous Armored Dinosaur, Nodosaurus 

 textilis Marsh ; by R. S. Lull (With Plates I to IV) . . 



Art. YIII. — Outline of the Application of the Theory of Space 

 Groups to the Study of the Structure of Crystals ; by R. 

 W. G. Wyckoff .... 



Art. IX. — Crystal Structure of Magnesium Oxide; by R. W. 

 G. Wyckoff 



Art. X. — Mississippian Fqrmations of the Horton- Windsor 

 District, Nova Scotia; by W. A. Belt 



Art. XI. — Relations of Subjacent Igneous Invasion to Re- 

 gional Metamorphism (continued); by J. Barrell 



Art. XII. — Permian of Coahuila, Northern Mexico; by E. 

 BosE 



Art. XIII. — Occurrence of Structures like Walcott's Algon- 

 kian Algae in the Permian of England ; by O. IIoltedahl 



97 ' 



127 ! 



138 : 



j 

 153 I 



174 



187 ! 



■I 



105 i 



SCIENTIFIC INTELLIGENCE. 



Chemiatry and Physics —Perchloric Acid as a Dehydrating Agent in the Deter- 

 mination of Silica, H. H. Willard and W. E. Coke": Chemistry and 

 Crystallography of Some Fluorides of Cobalt, Nickel, Manganese and 

 Copper, F. H. Edmister and H. C. Cooper, 207. — Notes on Chemical Re- 

 search, W, P. Dreaper : Elementary Chemistry for Coal-mining Students ; 

 L. T. O'Shea, 208. — Creative Chemistry, E. E. Slosson : Ou en est La 

 Meteorologie, A. Berget, 209. — Etude sur Le Svsteme Solaire, P. Reynaud, 

 210.— The National Physical Laboratory, Report for the Year 1919, 211. 



Geology and Mineralogy — Geology of Anglesey, E.' Greenly, 212. — Ahriss der 

 Allgemeiuen und Stratigraphischen Geologie, E. Kayser : Geology and 

 Mineral Resources of Bexar Co.. Texas, E. H. Sellards: Geology of Tarrant 

 County, W. M. Winton and W. S. Adkins : Mineralogy, an introduction 

 to the' Study of Minerals and Oi-ystals, E. H. Kraus and W. F. Hunt, 

 218.— Ore Deposits of Utah, B. S.' Butler, 214. 



Obituary— U. A. Bumstead : W. deW. Abney : P. S. Umfreville : W. A. 

 Howard : Y, Delage, 214. 



