142 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



that no others were so ; but some of the quadrupeds, it appears, are 

 almost equally entitled to this name, and the recently discovered 

 Otozoum is eminently pachydactylous, although probably a batra- 

 chian. 



2. Winged feet. — Two species of the pachydactylous animals 

 appear to me to have been wing-footed, like the American coot 

 and the grebe ; for the membrane seems to have extended to the 

 tip of the claw, as in the grebe. Their tracks are quite shallow, 

 and the toes of great width, as distinctly lobate as those of the 

 coot. The margin of the track appears as if a membrane had 

 made a slight impression ; but the whole depression has not that 

 rounded form which is exhibited in the other pachydactylous tracks. 

 Hence I have separated two species into a distinct genus on this 

 ground. And yet it is possible to conceive such to have been 

 the semifluid state of the mud when the track was made that 

 the bottom of the depression beneath the animal's foot filled up 

 in part, and the margin also partially slid inwards. Yet in such 

 case the claw, it seems to me, would be scarcely affected at all ; 

 whereas, in fact, the peculiarity above described is most striking in 

 that part of the track ; and at present 1 incline to the opinion, that 

 this character is to be relied upon for a generic distinction. 



3. Number of toes. — This would seem at first view to be one of 

 the best of characters ; since in living animals the number of toes 

 is rather constant in different classes of animals. But it requires 

 a good deal of care not to be deceived in respect to the actual num- 

 ber of toes in the fossil footmarks. In living animals, especially 

 birds, the hind toe is usually articulated to the tarso-metatarsus 

 above its extremity, so that it often does not reach the ground, or 

 only its extremity does so. And in the fossil footmarks we some- 

 times find that only the extreme point made an imjiression ; and 



