CONTENTS. 
PART I. 
I. On a Standard Voltaic Battery. By Latimer Clark, M.I.C.E. Communicated by 
Sir William Thomson, LL.D., F.R.S. page 1 
II. Researches in the Dynamics of a Rigid Body by the aid of the Theory of Screws. 
By Kobert Stawell Ball, LL D., Professor of Applied Mathematics and 
Mechanism in the Royal College of Science for Ireland. Communicated by 
Professor Cayley 15 
III. On the Organization of the Fossil Plants of the Coal-measures . — Part V. Astero- 
phy llites. By W. C. Williamson, F.R.S . , Professor of Natural History in the 
Owens College , Manchester . 41 
IV. On the Action of Electricity on Gases . — II. On the Electric Decomposition of 
Carbonic-acid Gas. By Sir B. C. Brodie, Bart., D.C.L., F.R.S., late Waynjlete 
Professor of Chemistry in the University of Oxford 83 
V. On the Anatomy and Histology of the Land-Planarians of Ceylon, with some 
Account of their HoMts, and a Description of two new Species, and with Notes on 
the Anatomy of some European Aguatic Species. By H. N. Moseley, M.A. Oxon. 
Communicated by G. Rolleston, M.D., Professor of Anatomy and Physiology in 
the University of Oxford 105 
YI. On a newly discovered Extinct Ungulate Mammal from Patagonia, Homalodonto- 
therium Cunninghami. By William Henry Flower, F.R.S. . . . . 173 
VII. On the Atmosphere as a Vehicle of Sound. By John Tyndall, D.C.L., LL.D., 
F.R.S. . . 183 
VIII. On the Fossil Mammals of Australia. — Part VIII. Family Macropodhle : 
Genera Macropus, Osphranter, Phascolagus, Sthenurus, and Protemnodon. By 
Professor Owen, F.R.S. &c 245 
IX. On the Structure and Development of the Skull in the Pig (Sus scrofa). By 
W. K. Parker, F.R.S. 289 
