A MONOGRAPH 



BEITISH STE0MAT0P0E0IDS. 



H. ALLEYNE NICHOLSON, M.D., D.Sc, Ph.D., E.G.S., 



REGIUS PEOFESSOE OP NATFEAL niSTOEY IN THE UNIVEESITY OF ABEEDEEN. 



PART I.— GENERAL INTRODUCTION. 



Pages i— iii, 1—130. Plates I— XI. 



LONDON : 



PEINTED FOR THE PAL^ONTOGEAPHICAL SOCIETY. 



1886. 



