42 EXPLANATION* OF PLATES 26 b . 27. 



Fig. 16. Recent track of a Pea-hen. 

 Fig. 17. Recent track of a domestic hen. 



Plate 26 b . 



Fig. 1. Ornithichnites giganteus. The natural cast here 

 figured represents the form and size of the foot, and 

 part of the claws. (Hitchcock.) 



Fig. 2. Ornithichnites diversus , with impressions of the 

 appendage to the heel, drawn from a plaster mould 

 sent by Prof. Hitchcock to the Geol. Soc. of London. 

 (Original.) 



Fig. 3. Track of a small animal on Oolitic slate near 

 Bath. See Journal of Royal Institution of London, 

 1831, p. 538, PI. 5. (Poulett Scrope.)* 



Plate 27. V. I. p. 205. 



Figs. 1 — 8. Tubercles and Scales, illustrating the four 

 new Orders of Fishes,, established by Professor 

 Agassiz. (Agassiz.) 



* Mr. Poulett Scrope has presented to the Geol. Soc. of London 

 a series of Slabs selected from the tile quarries worked in the Forest 

 Marble beds of the Oolite .formation near Bradford and Bath.: The 

 surface of these beds is covered with small undulations or ripple mark- 

 ings, such as are common on the sand of every shallow shore, and also 

 with numerous tracks of small animals (apparently Crustaceans) 

 which traversed the sand in various directions, whilst it was yet soft, 

 and covered with a thin film of clay. These footmarks are in double 

 lines parallel to each other, showing two indentations, as if formed 

 by small claws, and sometimes traces of a third claw. (See PI. 26 b , 

 Fig. 3.) There is often also a third line of tracks between the other 

 two, as if produced by the tail or stomach of the animal touching the 

 ground. Where the animal passed ovei the ridges of the ripple 

 markings or wrinkles on the sand, they are flattened and brushed 

 down. Thus a ridge between b. and d. (PI. 26>\ Fig. 3) has been 

 flattened, and there is a hollow at e. on the steep side of the ridge, 

 which may have been produced by the animal slipping down or climb- 

 ing up the acclivity. 



