[MATTHEW] NEW GENUS OF BATRACHIAN FOOTPRINTS lOS 



that it not infrequently takes on the appearance of a lobe rather than a 

 loe (though we know it to be undoubtedly tHie latter) and so is like many 

 Carboniferous tracks, where we are sometimes unable to determine 

 (whether a certain impression is due to a toe, or only to a projecting lobe 

 of the sole, such as is made by the " ball of the foot " in a human foot- 

 step. Nanopus quadratus and Baropezia Sydnensis are examples. 



The wide radiation of the toes in the mark of the fore foot in the 

 frog is also paralleled by the corresponding attitude of the toes of the 

 fore foot in many Carboniferous tracks; in this frog the area covered 

 is a semicircle, but in most Carboniferous tracks it is not more than a 

 quadrant (Megapezia Pineoi) ; however, this in many cases is due to the 

 lessened number of toes, which in the Carboniferous tracks is often 

 reduced to three. See Asperipes caudifer, A. avipes, A. flexilis, Baril- 

 lopus arctus, Cursipes Dawsoni. 



The track of the frog is essentially " digitigrade" (to use Sir Wm. 

 Dawson's expression), and finds its parallel in this respect in some 

 tracks referred to the genus Hylopus of Dawson. 



At plate 21 of Ichnographs of the sandstones of the Connecticut 

 River, Dr. Deane has given the track of a modern alligator in 

 v^^hich we have a set of footsteps coming under Dr. Dawson's class of 

 " plantigrade " ; the sole of both fore and hind foot is distinctly marked. 

 The offsetting or separateness of the fifth digit in the fore foot of this 

 animal is plain, but the corresponding digit is wanting in the track of 

 the hind foot. 



In the fore foot the radiation of the toes, as in the frog, covers a 

 semicircle, but if we should take off the two outer toes we should have 

 a grouping of the toes corresponding to that in the three toed species 

 of the Carboniferous, such as Barillopus arctus, Cursipes Dawsoni, 

 Megapezia Pineoi. We note, however, that in the alligator the toes of the 

 fore foot as a whole turn outward while those of the frog turn inward, 

 and this inward turning of the toes is the common arrangement in the 

 Carboniferous forms. See Hylopus Logani, Dromillopus erectus, 

 Nanopus obtusus, N. quadratus, Baropezia Sydnensis, B. abscissus. 



In the hind foot of the alligator there is the same preponderance 

 of size over the fore foot which is seen in the Carboniferous footprints; 

 and in both the fore and hind feet of the former the heavy mark made 

 by some of the phalanges is counterfeited by corresponding pits in the 

 fossil footprints. Hylopus caudifer, Barillopus arctus, Cursipes 

 Dawsoni, Baropezia Sydnensis, B. abscissus. Also the great size and 

 length of the sole in the footprint of the alligator are duplicated in 

 many Carboniferous tracks, Baropezia abscissus, Megapezia Pineoi, 

 !N"anopus quadratus; though this is not a universal character, the print 



