436 THE POPULAR SCIENCE MONTHLY. 



ly forward. The front is about one-third the size of this large hind- 

 foot, and the toes are arranged like those of the front-feet of the Her- 

 petoids. One of the species seems to have had a long, slender tail. 

 This batrachian must have been as large as an elephant, and exceeded 

 in size every other animal among the Ichnozoa. Imagine a frog as 

 large as an elephant, whether announcing the advent of spring by 

 piping, croaking at night in the summer, or taking gigantic leaps after 

 the manner of his modern representatives ! 



A very important character in the feet of frogs is the possession 

 of pellets, or knobs, instead of claws, at the ends of the toes. These 

 may be observed in the Otozoum, and all the other genera of this 

 group. One genus resembles the Cheirotherium in form, but not in 

 size, having a foot less than an inch long. None have the remarkably 

 long middle toes on the hind-foot, so characteristic of living frogs. 



A small, living salamander has the posterior feet pointing back- 

 ward ; and, as he walks, the toes point away from the head. The 

 track-way, therefore, consists of two parallel rows of footprints, half 

 of each pointing forward and half directed backward. This salaman- 

 der has its representative ichnozoan in the Stetiodactylus, not varying 

 essentially in size from it. 



One of the most interesting classes of batrachian impressions is 

 called Batrachoides. They consist of numerous saucer-shaped hollows 

 an inch in diameter, crowded together so thickly that the original oval 

 outlines have become pentagonal. Not unfrequently these saucers are 

 arranged in lines and squares, because parallel rows of ripple-marks 

 were occupied by the animals in their construction, often covering sev- 

 eral square yards of surface. 



Fig. 4. 



;rrT- rr^b"?- - - - ? - 



BrruKCtrLiPES. 



Whether arranged in order or clustered helter-skelter, these im- 

 pressions cannot be distinguished from the mud-nests made every sum- 

 mer by existing tadpoles. Hence it is natural to suppose that the 

 markings made at the different periods were produced by the same 

 agency ; and, as we know the origin of the latter, we may infer how 

 the first came upon the rocks. The chief difficulty in the way of ac- 

 cepting this view lies in the perfect resemblance between them. If 

 this doctrine is received, we must believe in the existence of tadpoles 

 in the carboniferous rocks, because they contain similar relics. Those 

 in the Triassic are remarkably distinct, making most beautiful speci- 

 mens for the show-case. 



The reference of the next group to the class of fishes may excite 



