[ -iv ] 
XX. On Mr. Spottiswoode’s Contact Problems. By W. K. Clifford, M.A., Professor 
of Applied Mathematics and Mechanics in University College , London. Commu- 
nicated by W. Spottiswoode, M.A., Treas. & V.P.B.S page 705 
XXI. On the Echinoidea of the ‘ Porcupine ’ Beep-sea Br edging Expeditions. By 
Professor Wyville Thomson, LL.B., B.Sc., F.B.S 719 
XXII. On the Structure and Bevelopment of Peripatus capensis. By H. N. Moseley, 
M.A., Naturalist to the ‘ Challenger ’ Expedition. Communicated by Professor 
Wyville Thomson, M.A., F.B.S . , &c., Birector of the Scientific Civilian Staff 
of the Expedition 757 
XXIII. On the Fossil Mammals of Australia . — Part IX. Family Macropodid^e : Genera 
Macropus, Pachysiagon, Leptosiagon, Procoptodon, and Palorchestes. By Pro- 
fessor Owen, F.B.S. &c. 783 
XXIV. Besearches in Spectrum- Analysis in connexion with the Spectrum of the Sum. 
— No. IV. By J. Norman Lockyer, F.B.S. 805 
Index 815 
