[ X ] 
X. On the Organization of the Fossil Plants of the Coal-measures. — Part IV. Dicty- 
oxylon, Lyginodendron, and Heterangium. By W. C. Williamson, F.B.S . , 
Professor of Natural History in Owens College, Manchester . . . page 377 
XI. Determination of the Number of Electrostatic Units in the Electromagnetic Unit 
made in the Physical Laboratory of Glasgow University. By Dugald MTviciian, 
M.A. Communicated by Sir William Thomson, F.B.S. &c. ..... 409 
XII. On the Minute Structure of the Leg -muscles of the Water-beetle. By Edward 
Albert Schafer. Communicated by Dr. Sharpey, V.P.B.S. ..... 429 
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