196 NATURAL SCIENCE [September 



which is not the case in the plate, nor in the specimen as now 

 mounted. 



My grateful acknowledgments are due to Sir William Flower, 

 K.C.B., for permission to reproduce these figures for publication, 

 and to Mr A. Smith Woodward, assistant keeper of the Geological 

 Department, for sundry hints and advice during the construction of 

 the diagrams. W. G. Ridewood. 



