﻿Ixii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



present a singularly perfect counterpart of many of the old triassic 

 shales above described. 



Mr. Darwin tells us in his f Journal of a Voyage in the Beagle? 

 that the South American ostriches, although they live on vegetable 

 matter, such as roots and grass, are repeatedly seen at Bahia Blanca, 

 lat. 39° S., on the coast of Buenos Ayres, coming down at low water 

 to the extensive mud-banks, which are then dry, for the sake of 

 feeding on small fish. Over such mud-flats, birds of different sizes, 

 together with alligators, turtles, and other reptiles, may wander and 

 leave their foot-prints, and yet, although swarming by myriads, may 

 leave none of their bones in the newly deposited sediment. I have 

 searched in vain, year after year, in the shell-marl of Scotland, for 

 the evidence of the existence of a single bird, in a deposit made up 

 bodily of shells of the genera Lymneus, Planorbis, Succinea, and Val- 

 vata, and in which the skeletons of deer, oxen, and other quadrupeds 

 are met with in considerable numbers, although we know that before 

 the lakes were drained, which yield this marl so largely used in agricul- 

 ture, the surface of the waters and the bordering swamps were covered 

 with the wild duck and wild swan, and with teal, herons, curlews, 

 snipes, and other fowl. They have left no fossil memorials behind 

 them, because if they perished on the land, their bodies decomposed or 

 became the prey of carnivorous animals ; if on the water, they were 

 buoyant and floated till they were devoured by predaceous fish or 

 birds, and in warmer countries by reptiles, such as the alligator. But 

 the same causes of obliteration have no power to efface the foot-prints 

 which such creatures may have left on an ancient mud-bank or shore, 

 and these, like the ripple-mark on the surface, or the casts of crevices 

 formed by the shrinkage of mud during desiccation, may be as im- 

 perishable as any other portion of the solid rock. 



We have at present no fossil remains of birds in the primary forma- 

 tions of any country, and none in the secondary, except the impres- 

 sions, above alluded to, in the red sandstone of New England, and a 

 few British specimens of bones from the oolite of Stonesfield and the 

 Wealden of Tilgate Forest. After I had been informed by Mr. Bower- 

 bank that among several bones of Pterodactyls from Stonesfield he 

 had met with one from the same locality which by its microscopic 

 structure was clearly referable to a bird, I proposed to Mr. Quekett 

 of the College of Surgeons to examine the fossils of the same class 



