456 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juue 21, 



locality (Paris), the calcaire grassier rests on the aryile plastufie, 

 and this on the Chalk, as the equivalents of the Lower Bagshots and 

 the Thanet Sands are here wanting. 



2. On the Ornithoidichnites of the Wealden. 

 By S. H. Beckles, Esq., F.G.S. 



[Plate XIX.] 



In two former papers communicated to the Geological Society* I 

 observed that certain large trifid bodies, presenting a resemblance 

 to the casts of the impressions of birds' feet, were numerous in the 

 cliffs to the east and west of Hastings : and I suggested, from cer- 

 tain uniform peculiarities which these gigantic tridactyle impressions, 

 or rather casts of impressions exhibited, that they might be really 

 foot-marks of birds. 



Up to the date of my first notice, my discoveries of these colossal 

 casts were limited to the east of Hastings and Bulverhithe, but my 

 continued investigations enabled me to announce in ray second com- 

 munication that I had successfully traced them through the entire 

 section of the Wealden rocks exposed on the coast, from Cliff 's-end 

 on the east of Hastings to Pevensey Sluice on the west. 



Although these tridactyle casts were collectively numerous, they 

 occurred for the most part on detached blocks of sandstone, and 

 never on a surface sufficiently large to admit of three or four con- 

 secutive marks ; and, although their number and regularity of form 

 afforded good presumptive evidence of their being organic in their 

 origin, yet these circumstances were insufficient to establish a truth 

 where sequence of arrangement, distinct evidence of a phalangeal 

 structure, or some other organic characters were indispensable ; 

 hitherto, therefore, these trifid bodies were not supposed to fulfil the 

 necessary conditions oi footmarks. 



The uniformity of character, however, in the casts that I first 

 examined had such an obvious connexion with a definite cause, as to 

 convince me that they were either of organic origin, or the result of 

 a uniform crystalline action ; I knew of no mineral law by which to 

 account for them, and I adopted the alternative -j*. 



* Quart. Journ. Geol. Soc. vol. vii. p. 117; and ibid. vol. viii. p. 396. The oc- 

 currence of similar bodies found by Mr. Saxby, in the Isle of Wight, is alluded to 

 by the late Dr. Mantell in his " Geol. Isle of Wight," &c. p. 247. ^Ir. Tagart's 

 specimen (see Quart. Journ. Geol. Soc. vol. ii. p. 267) is in the Museum of the 

 Geological Society ; and a similar example is in the British Museum. In the 

 Society's Collection there is also a large slab of Purbeck limestone, the surface of 

 which is shaly and covered with coarse fucoidal (.') markings. In this shaly por- 

 tion are two large, trifid, pachydactylous foot-marks, resembling those from the 

 Wealden, each measuring 12 inches in length. 



t With the extensive accumulation of these natural casts in my collection, I 

 felt much surprise that men of real science should still pronounce them mere 

 accidental concretions. The cause, whatever it was, so uniformly produced the same 

 effects, whether in clay-rock, sandstone, or shale, as to be inconsistent with our 

 idea of an accident. To reject these trifid bodies as organic ph;enomena, because 



