280 PICTURESQUE SKETCHES 



a few marine turtles exhibiting some interesting 

 peculiarities, and connecting the freshwater and ma- 

 rine tribes ; but most of the marine species are smaller 

 than those now existing, and resemble species re- 

 stricted to warm climates. 



The serpents of the London clay are extremely 

 interesting, for they are of the tribe now represented 

 by the boa constrictor and python, and attained un- 

 questionably very large dimensions, varying, probably, 

 from ten to upwards of twenty feet in length. Rep- 

 tiles of this kind only exist at present in tropical coun- 

 tries, and they generally prey on quadrupeds and birds. 



The fossil remains of birds from the older tertiaries 

 are exceedingly rare, owing, no doubt, chiefly to the 

 fact, that the fragments of such animals would be 

 rarely conveyed to the sea or estuary where a deposit 

 was going on. Still the London clay of Sheppey has 

 yielded proof of the existence of more than one species 

 of bird which inhabited the land at the time of this 

 deposit, and amongst them is a true vulture, smaller 

 than any now known to exist. 



Although the remains of birds are very rare in the 

 marine formation of the London clay, several species 

 have been obtained from the examination of the Paris 

 Basin fossils, some of which more or less resemble 

 the pelican, the sea-lark, the curlew, the woodcock, 

 the owl, the buzzard, or the quail. In a few in- 

 stances the general outline of the skeleton has been 

 preserved. 



We next have to consider the land quadrupeds 

 characteristic of these strata. Such fossils are much 

 more commonly found in the gypsum beds near Paris 

 than in the London clay ; but this has no doubt arisen 



