' 68 Etheridge — Stratigraphical position 



in the Lower Chalk of either Europe or England ; whereas in the 

 Wealden group below the true Cretaceous rocks, and still lower, in 

 the Oolites and Lias, many genera occur. The discovery by the 

 Eev. W. Fox of a remarkable and allied reptile in 1866, from the 

 Wealden beds of the Isle of Wight, named Polacanthus by Pro- 

 fessor Owen, increases still more the interest of this new genus, 

 and is another reason why it is well to understand its geological 

 horizon. 



The remains were found in the autumn of the past year in the 

 lower part of the Chalk Marl immediately east of Copt Point, Folke- 

 stone. The beds of the Lower Chalk here are much disturbed and 

 pushed out of place, owing, doubtless, to the unctuous nature of the 

 Gault which underlies the sandy Upper Greensand ; and the Lower 

 Hard Chalk, owing to its great superincumbent weight, has slid 

 over and here pressed up the Gault and Upper Greensand seaward, 

 thus giving a faulted appearance along a line from east to west ; it is, 

 however, superincumbent pressure only that has produced the 

 crumpling and apparently reversed dip of the Gault, Upper Green- 

 sand, and the lower members of the Chalk. The true position of 

 the whole series is admirably exhibited and easily understood along 

 the shore to the eastward under Lyddon's Spout, etc. 



The sequence of the beds near Copt Point, where the Eeptilian 

 remains were found, was at first difficult clearly to understand, from 

 the circumstance of their occurring between high and low water 

 mark, and the denuding agency of the sea, along the strike, or 

 exposed edges of the beds which dip north, or towards the cliff, is 

 constantly destroying the soft Upper Greensand and yielding Lower 

 Chalk. 



I was, however, enabled clearly to determine the true place of the 

 fossil, and also its associated fauna. From the same bed I listed no 

 less than forty species, comprising Amorphozoa, Echinodermata, Mol- 

 lusca, and the remains of another reptile, Ichthyosaurus campylodon. 



At Copt Point the Gault may be about 100 feet in thickness, pre- 

 ceded by (when moist) the dark-green sandy Upper Greensand, which 

 is from fifteen to twenty feet thick, and at the upper part cuts 

 a bright copper-green colour. This Upper Greensand is immedi- 

 ately succeeded by the hard, dense, pale-grey Chalk Marl, which 

 becomes nearly white when deprived of its moisture. It was in the 

 lower part of this, and about eight feet above the Upper Greensand, 

 that the remains of Acanihojpholis horridus were found by Mr. Griffiths, 

 portions of which ultimately came into Professor Huxley's posses- 

 sion through Dr. Percy : their affinities were immediately recognised, 

 but the characters being different to any known genus no pains were 

 spared to obtain as much as possible of the remaining skeleton, and, 

 although in a fragmentary state, yet enough has been obtained to 

 establish the genus. 



My attention, on visiting the section, was immediately turned to 

 the associated fossils, which clearly determine the age and position 

 of the remains, and definitely fix it as belonging to the lower part 

 of the Grey Chalk series, (the Chalk Marl with Brachiolithes) and the 



