338 PALAEONTOLOGY. 



the law of correlation of animal structures may be successfully 

 applied, and indicates the instances in which — the physiolo- 

 gical condition being unknown, and the coincident structures 

 being understood empirically — careful observation and rigor- 

 ous comparison must supply the place of the physiologically 

 understood law. 



Those who deny the existence of design in the construction 

 of any part of an organized body, and who protest against the 

 deduction of a purpose from the valves of the veins or the lens 

 of the eye-ball, repudiate the reasoning which the palaeonto- 

 logist carries out from the hoof to the grinder, or from the 

 carnassial molar to the retractile claw, through the guidance 

 of the principle of a pre-ordained mutual adaptation of such 

 parts ; but such minds are not, nor have been, those who have 

 contributed to the real advancement of physiology or palaeon- 

 tology. 



By reference to the " Table of Strata" (fig. 1), it will be 

 seen that the earliest evidence of a vertebrate animal is of the 

 cold-blooded water-breathing class in the upper Silurian period. 

 Next follows that of a cold-blooded but air-breathing verte- 

 brate, under the batrachian grade, in the carboniferous period. 

 The warm-blooded air-breathing classes are first indicated, as 

 birds, by footmarks in a sandstone of probably triassic but 

 not older age ; and, as mammals, by fossil teeth from bone- 

 beds of the upper triassic system in Wirtemberg, and of, appa- 

 rently, the same age near Frome, Somersetshire. Mammalian 

 remains have also been found in a coal-field in North Carolina, 

 which may be earlier, but cannot be later, than the lias forma- 

 tion. 



Genus Microlestes. — The mammalian teeth from German 

 and English trias indicate a very small insectivorous quad- 

 ruped, to which the above generic name was given by Pro- 

 fessor Plieninger. The German specimens were discovered in 

 1847 in a bone breccia at Diegerloch, about two miles from 



