ANTIQUITY OF FOSSIL BIRDS. 669 



contemporaneous with strata generally classed by geologists as Upper 

 Silurian. 



The imagination may well take alarm at the confusion which we may 

 expect to encounter in settling sundry questions of Geological chronol- 

 ogy, when we have to deal with ancient deposits found on the frontiers 

 of distinct Natural History provinces. But it is consolatory to reflect 

 that all this ambiguity will arise out of the strict agreement prevailing 

 between the present and ancient condition of the globe, and the laws 

 governing the changes of its surface, whether they be those of the ani- 

 mate or inanimate world. So long as we feel sure that in existing na- 

 ture we have a key for interpreting the mysteries of the past, we need 

 never despair ; whereas, had the causes acting in the remoter ages differ- 

 ed either in kind or degree from those now operating, our science must 

 forever have continued one of mere conjecture and ingenious speculation. 



ANTIQUITY OF FOSSIL BIRDS (p. 456). 



Since the table printed at p. 456 was compiled (in 1854), the records 

 of this great class of Vertebrata can be carried back somewhat farther 

 in time, or one step lower down in the Tertiary series. Early in 1855 

 the tibia and femur of a large bird equalling at least the ostrich in size 

 were found at Meudon near Paris, at the base of the Plastic clay. This 

 bird, to which the name of Gastornis Parisiensis has been assigned, ap- 

 pears, from the Memoirs of MM. Hebert, Lartet, and Owen, to belong to 

 an extinct genus. Professor Owen refers it to the class of wading land- 

 birds rather than to an aquatic species.* 



That a formation so much explored for economical purposes as the 

 Argile Plastique around Paris, and the clays and sands of corresponding 

 age near London, should never have afforded any vestige of a feathered 

 biped previously to the year 1855, shows what diligent search and what 

 skill in osteological interpretation are required before the existence of 

 birds of remote ages can be proved by more decisive evidence than their 

 supposed foot-prints. 



* Quart. Geol. Journ., vol. xii. p. 204, 1856. 



