50 Notes on Wiltshire Geology and Paleontology. 



The Oxford Clay, next in order, is continuous from the Dorsetshire 

 coast all the way to Scarborough ; and extended through Wiltshire 

 as a level belt, occasionally five or six miles broad, and having a thick- 

 ness of about 600 feet. It consists chiefly of thinly laminated 

 marls, which are seldom opened up, except in pits for brick -making. 

 Owing to this much is lost to the palaeontologist, as the beds are 

 crowded with organic remains, many of which are of high interest, 

 and include Ichthyosaurus, Pliosatmis, and Steneosaurus, many of 

 large size. But the harvest times as regarded this formation were 

 in the days of my friend Pearce, for then the Great Western Railway 

 was in course of construction, and on either side of the line between 

 Chippenham and Wootton Bassett pits may be seen — now mostly 

 filled with water — from which the laminated marls were extracted be- 

 low a covering of mammal drift gravels. These marls were crowded 

 with Ammonites, the shells of which still possessed their perfect 

 terminations, a feature rarely seen in other formations. Belemnites 

 —•the internal shells of an animal allied to the cuttle fish — abounded, 

 and the cuttle fish also, so perfect that its cuttle bone remains, its 

 original fluid ink is preserved, and on its extended arms are still 

 arrayed the horny hooks and suckers used in capturing its prey. 

 Another unique specimen, from Christian Malford, was a colony of 

 barnacles, that still remained attached to its stalk. Crustaceaa of 

 peculiar form and fish were also plentiful. Had I been a landowner 

 on the Oxford Clay I should long since have been tempted to open 

 some pits for the ancient natural history they would have revealed. 



In most of the beds containing Ammonites a curious triangular 

 bivalve body is found called Trigonellites. It occurs in the Oxford 

 Clay, but more plentifully in the Kimmeridge beds. They are more 

 often found free, but occasionally in the outer chamber of the Am- 

 monite itself. No organism, probably, has been a greater puzzle to 

 palaeontologists. By some authors they have been supposed to be 

 bivalve shells, and named Aptychus, Munsteria } and Cirripedes — by 

 others the gizzards of the Ammonite, or the operculum of that 

 shell, the last view being that now generally adopted, though I have 

 some reasons for believing that eventually this will not be found 

 correct. 



