hertfordshiee natural history society. ixv 



Field Meeting, 25th Jiine, 1881. 

 TOTTERXnOE, KEXSWORTII, AND LUTOX. 



The Dimstablo Dovrns form the most elevated tract of country 

 north of London -within the area of the Chalk formation, in the 

 trough of which lies the London Tertiary Basin, their highest 

 point, Kensworth Hill, being at least 800 feet above sea-level. 

 The Chalk here forms two escarpments, but the higher beds of the 

 Upper Chalk are not represented, the main escarpment exposing 

 the outcrop of the Lower Chalk and the lower beds of the Upper 

 Chalk, and the secondazy escarpment the lower beds of the Lower 

 Chalk and the upper portion of the Chalk Marl, with the Tottem- 

 hoe Stone forming its highest bed. 



To gain a knowledge of the physical features of the Dunstable 

 Downs and surrounding country, and to examine the Totternhoe 

 Stone, which only occurs on the north-west outcrop of the Chalk 

 Marl, the members of the Geologists' Association, the Hertfordshire 

 Natural History Society, and the Luton Natural History Society, 

 assembled at Stanbridgeford Station at about half -past 11, and at 

 once proceeded, some in carriages and some on foot, to the Tot- 

 ternhoe quarries, where a good section of the Totternhoe Stone is 

 exposed. 



Mr. Saunders here said that this bed usually occurred in two 

 seams, each about three feet thick, and consisted of a compact 

 arenaceous limestone, which, in working, separated into massive 

 blocks. Its sandy nature suggested a break in the continuity of 

 the physical conditions which accompanied the deposition of the 

 other beds of the Chalk formation, which were almost purely cal- 

 careous. The Totternhoe Stone played an important part in modi- 

 fying the physical features of the district. At its junction with 

 the overlying bed many springs took their rise, the long-continued 

 action of which had been the primary agent in excavating those 

 coombs or valleys which were so characteristic of chalk escarp- 

 ments. Of these escarpments examj)les might be seen at Ivinghoe, 

 Barton, Ravensbury Castle, and Pegsdon Barns. Of the rarer 

 fossils found in this bed, Mr. Saunders mentioned that he had dis- 

 covered part of the jaw, with teeth, of Ichthyosaurus campylodon, 

 and a crustacean, Palcega Carteri, the first of its kind which ex- 

 hibited the caudal appendages by which Dr. Henry Woodward was 

 enabled to determine the affinities of the species. 



Rain had fallen heavily in the morning, and now it again de- 

 scended, rendering fossil-collecting not such a pleasant occupation 

 as it would otherwise have been. A good many fossils were, how- 

 ever, found, including Rhynchonella plicatula and R. octoplicata, 

 Terehratulce, Inocerami, etc., teeth of Ptychodus, and a fragment of 

 a large dorsal spine of a sauroid fish, the only important find. 

 Some nodules of chert were also obtained. 



The party then walked across the fields to Totternhoe Knoll, on 

 the summit of which Professor Morris gave an address on the 



VOL. I. — PART VIII. F 



