VI.] 



SPECIES AND TIME. 



149 



Moreover, if the remarkable and minute similarity of the 

 coracoid of a pterodactyle to that of a bird be merely the 

 result of function and no sign of genetic affinity, it is not 

 inconceivable that the pelvic and leg resemblances of 



THE ARCHEOPTERYX (OF THE OOLITE STRATA). 



Dinosauria to birds may be functional likewise, though 

 such an explanation is, of course, by no means necessary 

 to support the view maintained in this book. 



But the number of forms represented by many indi- 

 viduals, yet by no transitional ones, is so gre 



SKELETON OF AN ICHTHYOSAURUS. 



two or three can be selected as examples. Thus those 

 remarkable fossil reptiles, the Ichthyosauria and Plesio- 

 sauria, extended, through the secondary period, probably 



