458 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 15, 



The impression of the fourth toe is shorter than that of the third ; 

 but, as the ungual phalanx is of nearly the same length as in the 

 third, the shortening would appear to be due either to the shorten- 

 ing, or to the smaller number, of the proximal phalanges. 



The impression of the fifth digit does not quite reach to the base 

 of the ungual phalanx of the fourth. The impression of the ter- 

 minal phalanx is less distinct, and, like the fourth, the stirring up 

 of the sand has rendered it indistinct at its proximal end. 



The surfaces of the interspaces between the digits are so peculiarly- 

 rounded that there can be little doubt they were moulded by a con- 

 necting membrane or web, though the precise boundaries of this 

 interdigital membrane are not traceable. 



{Hind Foot.) — The ends of the toes of the posterior impression of 

 the pair to which that just described belongs infringe upon the pos- 

 terior and outer part of the plantar margin of the anterior impres- 

 sion. It is but a confused mark, however, and the true characters 

 of the imprint left by the hind foot are much better shown in the 

 pair behind these, where the sand was evidently firmer when the 

 animal walked over the surface. 



This impression (fig. 5) measures about 2^ inches transversely, 

 and longitudinally 2J inches, or a little less. 



The plantar surface measures 1\ inch from before backwards, 

 and its posterior edge is nearly semicircular and not emarginated. 

 The anterior edge is nearly straight. It gives off four deepish lon- 

 gitudinal impressions, answering to as many digits. Of these the 

 middle two measure 1-|- inch in length, and are consequently some- 

 what longer than the inner and the outer, which are har(fiy more 

 than -I inch long. 



The ungual phalanges appear not to have attained a length of |-ths 

 of an inch in the longest digits, and all four digits appear to have 

 been connected by a web. The anterior and external angle of the 

 plantar surface projects fths of an inch beyond the base of the 

 fourth digit, as if there had been a rudimentary fifth digit, 



The length of the stride, from the hinder edge of one fore-foot 

 print to that of the next, is just twelve inches. The space covered 

 by the track transversely to its length, measured from the outer edge 

 of one foot-mark to a line prolonging that of the foot-mark on the 

 opposite side, is about ten inches. 



On the same slab as that on which these tracks occur there are a 

 number of other foot-marks, some of which are nearly eight inches 

 long, while others hardly exceed an inch in length. They are aU, 

 however, more or less imperfect, either from the condition of the 

 surface at the time they were impressed, or from the subsequent 

 superposition of other impressions. The only feature which they 

 exhibit better than those just described is the mark of the inter- 

 digital membrane, which in some of these foot-marks is very obvious, 

 and exhibits strong transverse wrinkles, concave forwards. 



All the other foot-tracks from Cummingstone which have come 

 under my notice are either mere unintelligible marks, or may be 

 explained by the perfect footsteps I have just described ; so that at 



