THE INDIGENOUS FAUNA. 17 



(see the record of Prof. Seeley, "Index to the Reptilia, etc., in the 

 Woodwardian Museum," Cambridge, 1869). 



An important difference of opinion exists as to the age of these 

 vertebrate fossils, Prof. H. G. Seeley believing that they were all 

 living in the Neocomian sea and the neighbouring lands, while 

 Mr Walker regards them as beiny; derived from the denudation of 

 the Kimmeridge clay, Wealden, and other rocks. The latter is, at 

 present, the generally received theory, but we shall, I think, find 

 reason to believe that our Neocomian bones belong to both these 

 sets, some of them being 'derived,' while a great many of them 

 really lived during the period when their present rock matrix was 

 being deposited. 



Many of the fossil teeth, both of Reptiles and Fishes, are 

 identical with well-known Kimmeridgian species, and yet they 

 are often remarkably free from marks of wave-rolling. 



My impression for a long time was that the vertebrate remains 

 were, with few exceptions, derived fossils, but more recently the 

 arguments of the general likelihood of such reptiles as the Iguano- 

 donts, Crocodiles, and Saurians having lived on the shores and 

 neighbouring land, together with the good state of preservation of 

 the specimens, have led me to believe that many of them are 

 proper to the bed in which we find them. — Still more weighty 

 evidence is the occurrence of certain species (Sphgerodus Neoco- 

 miensis, Pycnodus, etc.) in various other Neocomian areas, widely 

 separated from one another, as, namely, Cambridgeshire, Bedford- 

 shire, and Shanklin (I. W.) in Britain ; the Perte du Rhone, 

 Landeron and elsewhere in Switzerland; and Alais (Gard), and 

 Auxerre (Aube) in France. This cannot be due to the mere 

 accident of specimens being washed out of older formations, for 

 the surrounding and underlying rocks in these places are quite 

 different and unsuitable. 



Again, these fossils are extremely rare in the Jurassic rocks 

 (I have never seen a specimen of Sphcvrodus gigas from the Jurassic 

 rocks of the Eastern counties), whereas in the Neocomian beds 

 they are, some of them, quite abundant ; nor is there any such 

 correspondence in proportionate numbers and species in the two 

 formations, the Neocomian and the Jurassic, as should surely 

 k. 2 



\ 



-' 



