169 



condition of the land, may have acted against the propaga- 

 tion of hfe over immense tracts, and account for the rarity 

 of organisms in our British strata ; or the extinction of all 

 the Pala30zoic races may have left a sterility in nature 

 over extensive regions, awaiting the dispersion of ncAv 

 forms of life from peculiar centres, such as the Muschel- 

 kalk, where we obtain a rich variety of Mesozoic life. 

 The Trias was probably dislocated and elevated soon 

 after its deposition, when the most prominent geogra- 

 phical features of the higli land of the British Islands 

 received its present character, later disturbances merely 

 affecting its general level. 



Ascending to the Oolitic system, we find all the classes 

 of the animal kingdom represented excepting Pteropoda. 

 The first example of pedunculated Cirrhipedia is found 

 in the Stonesfield slate ; the sessile Cirrhipedia have not 

 been noticed in Mesozoic strata. Of Insecta, Coleoptera 

 and Neuroptera are found in the Inferior Oolite, Lias, 

 and Wealden strata ; these two orders, and Orthoptera, 

 Homoptera, and Diptera, in the Lias and Wealden only. 

 Insect remains occur also in the Kimmeridge clay. Prob- 

 lematical bones of Birds have been found in Stonesfield 

 slate. Inferior Oolite ; an observation authenticated in 

 remains from the Wealden. The occurrence of the foot- 

 prints of Birds, however, indicate their existence from 

 the Triassic epoch. In this system it is interesting to 

 find the earliest evidence of Mammalia. The lower jaws, 

 with teeth attached, of Marsupials, have been found at 

 Stonesfield in the Inferior Oolite,* and in the Purbeck or 

 Wealden strata ;t and on the continent, mammalian molar 

 teeth and fragments of bone have been found, in a bone 

 breccia, at Wurtemburg — strata corresponding to the 

 bone bed of our Lias at Aust. 



• Amphithcrium, Phascolotherium, &c. 

 + Spalaeothcrium, and tliiiteen new species. — Lyull'a Ekmcnls, 1857. 



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