THE CRETACEOUS PERIOD. 283 



aquatic members of the class of Birds with which we are ac- 

 quainted at the present day. It appears to have stood between 

 five and six feet high, and its inability to fly is fully compen- 

 sated for by the numerous adaptations of its structure to a 

 watery life. Its teeth prove it to have been carnivorous in its 

 habits, and it probably lived upon fishes. It is a curious fact 

 that two Birds agreeing with one another in the wholly abnor- 

 mal character of possessing teeth, and in other respects so 

 entirely different, should, like Ichthyornis and Hesperornis, 

 have lived not only in the same geological period, but also in 

 the same geographical area ; and it is equally curious that 

 the area inhabited by these toothed Birds should at the same 

 time have been tenanted by winged and bird-like Reptiles 

 belonging to the toothed genus Pterodactyl us and the toothless 

 genus Pteranodon. 



No remains of Mammals, finally, have as yet been detected 

 in any sedimentary accumulations of Cretaceous age. 



LITERATURE. 



The following list comprises some of the more important works and 

 memoirs which may be consulted with reference to the Cretaceous strata 

 and their fossil contents : 



(1) ' Memoirs of the Geological Survey of Great Britain.' 



(2) 'Geology of England and Wales.' Conybeare and Phillips. 



(3) ' Geology of Yorkshire,' vol. ii. Phillips. 



(4) 'Geology of Oxford and the Thames Valley.' Phillips. 



(5) ' Geological Excursions through the Isle of Wight.' Mantell. 



(6) 'Geology of Sussex.' Mantell. 



(7) ' Report on Londonderry,' &c. Portlock. 



(8) ' Recherches sur le Terrain Cretace Superieur de TAngleterre et de 



1'Irlande.' Barrois. 



(9) "Geological Survey of Canada" 'Report of Progress, 1872-73.' 

 (10) 'Geological Survey of California.' Whitney. 



(n) 'Geological Survey of Montana, Idaho, Wyoming, and Utah.' 

 Hayden and Meek. 



(12) 'Report on Geology,' &c. (British North American Boundary 



Commission). G. M. Dawson. 



(13) ' Manual of Geology.' Dana. 



(14) ' Lethaea Rossica. ' Eichwald. 



(15) ' Petrefacta Germanise.' Goldfuss. 



(16) 'Fossils of the South Downs.' Mantell. 



(17) 'Medals of Creation.' Mantell. 

 '\l&) ' Mineral Conchology.' Sowerby. 



(19) 'Lethaea Geognostica.' Bronn. 



(20) ' Malacostracous Crustacea of the British Cretaceous Formation' 



(Palseontographical Society). Bell. 



(21) ' Brachiopoda of the Cretaceous Formation' (Palseontographical 



Society). Davidson. 



(22) 'Corals of the Cretaceous Formation' (Palaeontographical Society). 



Mi' ne-Ed wards and Haime. 



