Geology and Natural History. 405 



so obscure that there is a reasonable doubt as to the correctness 

 of its interpretation. In one instance a dragging tail is shown 

 which is absent in all other specimens and which is evidence in 

 favor of the belief that the animal is a biped. Otozoum has the 

 largest track of all, measuring twenty inches in length, but the 

 author has no conception of the appearance of the creature itself. 



Among the so-called leptodactylous or narrow-toed tracks, are 

 many made by bipedal forms which were doubtless dinosaurs, 

 some carnivorous, and some, judging from the manus which is 

 occasionally seen, herbivorous in habits. The subsequent slip- 

 ping 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 identi- 

 cal with known forms, while still others 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 represented is proportionately 

 small, and these are mainly from one or two localities. 



Of the truly quadrupedal forms the most interesting is Batra- 

 chopus, 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 Batra- 

 chopus 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 quadrupedal 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 date whereon to base a 

 theory as to their affinities. Professor Osborn has likened ichno- 

 logical 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." 



3. The Non-metallic Minerals ; their Occurrence and Uses ; 

 by George P. Merrill, Head Curator of Geology in the TJ. S. 

 National Museum, etc. Pp. xi, 414. New York, 1904 (John 

 Wiley & Sons). — This work has grown out of the author's Guide 

 to the Collections in Applied Geology in the U. S. National 

 Museum. While it does not attempt to be a complete text-book, 

 it brings together a large amount of interesting data in regard 



