EXPLANATION OF THE PLATES AND WOOD-CUTS. 



PLATES XXVIL and XXVIIL 



To illustrate Mr. Murchison and Mr. Strickland's Memoir on the tipper Formations of 

 the New Red Sandstone System in Gloucestershire, &c. : p. 331. 



Plate XXVIL 



Map and Sections : p. 331. et seq. 



Plate XXVIIL 



(Fossils from the Keuper Sandstein, p. 338.) 



Pig' 1. Ripple marks and impressions of footsteps on a slab of sandstone from 

 Shrewley Common, Warwickshire, one-third the natural size. The impressions 

 are in relief. The slab is preserved in the Warwick Museum ; but a portion of the 

 counterpart is in the Museum of the Geological Society : p. 339. 



The footsteps were formed by an animal which was probably allied to the Batra- 

 chians. The toes appear to have been destitute of claws, and the larger or pos- 

 terior foot exhibits faint traces of having been vrebbed. In these respects and in 

 their general form they have some resemblance to the feet of frogs, but differ from 

 them in having the outer toe of both the hind and fore feet longest, while in frogs 

 the second toe is the longest. It is moreover evident, that this animal possessed a 

 tail, which dragging in the soft sand, has caused a groove, about | of an inch wide, 

 intermediate between the alternate footsteps. This groove meanders slightly from 

 side to side, approaching each pair of footsteps alternately. 



The impressions of the feet are repeated twelve times, at equal intervals of 

 about 9^ inches. To this, however, there are two exceptions, — the distance from 

 a to b in fig. 1. being only 6 inches, and from c to d 7 inches. We may conjec- 

 ture that the animal stopped for a time at this point, and then proceeded, an opi- 

 nion which is confirmed by the semicircular ridge of sand marked e, which may 

 have been formed by the under side of the animal, or by the impulse necessary for 

 the resumption of his motion. Several smaller impressions of similar footsteps may 

 be detected on the surface of the slab ; four of them markedy, g, h, i, are in regular 

 alternate succession ; the others, marked k, are in no regular order, the impressions 

 corresponding to them being too faint to be detected. 



A considerable resemblance exists between these impressions and some which 

 have since been discovered (in company with those of the Cheirotherium) in the 

 Bunter Sandstein at Storeton Hill, near Liverpool ; also at Grinshill near Shrews- 

 bury, specimens of which latter are in the Museum of that town. 

 Fig. 2. A pair of footsteps of the natural size marked with a star on fig. L 

 Fig. 3. An Ichthyodorulite of Hi/bodus Keiqieri (Murch. and Strick.) from Burgehill, 

 now in the Museum of the Geological Society. 



This Ichthyodoruhte was nearly perfect when the description at p. 338 was 

 written, but having been since unfortunately injured, we are able to show only the 

 fibrous structure of the interior in fig. 3, the external costae on the lower side 



