')46 RICHARD SWANN LULL ON 



manus which is occasionally seen, herbivorous in habits. The subsequent slipping of the 

 mud after the withdrawal of the foot has obliterated most of the morphological characters 

 from the impressions. Some of the leptodactylous forms have been identified with the 

 better known genera and species, others which cannot be so identified because of their 

 obscurity may nevertheless be identical with known forms, while still (jthers evidently do 

 not occur elsewhere. It is a notable fact that while the number of genera and species 

 which have been erected upon these impressions is large, the number of individuals repre- 

 sented is proportionately small and these are mainly from one or two localities. 



Of the truly quadrupedal forms the most interesting is Batrachopus. whose long- 

 limbs, tetradactyl, plantigrade pes with acuminate claws, and phalangeal formula of 2. 3. 4. 

 5, and whose pentadactyl manus are such as one would expect to find in the dinosaurian 

 ancestor. It seems possible therefore, that Batrachopus represents a persistent type 

 whose affinities are near the dinosaur stem form and which should be classed with Kadalio- 

 saurus in the superorder Diaptosauria of Osborn. Batrachopus may have been a true 

 dinosaur which had retained, among other primitive characters, the ancestral ({uadrupedal 

 gait. The mode of progression was a true walk like that of a mammal and not the 

 sprawling crawl of modern reptiles. Batrachopus included small forms of carnivorous 

 habits. 



There remain other quadrupedal forms, generally of small size, whose tracks, aside 

 from the number of digits, size of the foot, and the length of limb, afford almost no data 

 whereon to base a theory as to their affinities. Professor Osborn has likened ichnological 

 interpretation to the deciphering of ancient cuneiform inscriptions which are utterly 

 unintelligible unless one possesses the key. That the key to the deciphering of the 

 dinosauroid tracks has been found seems evident, but in the attempt at the interpretation 

 of the obscurer quadrupedal footprints the student is still very much in the dark. 



Amherst, Mass. 



