SECTIONAL TRANSACTIONS— C. 413 



it was entirely peasant in character. No administrative centre is known, 

 but this may have been at Durobrivae (Castor-Water Newton) on the 

 western fringe of the region. There is no positive evidence of Roman 

 drainage works on any scale, and the occupation and abandonment of the 

 region appears to have depended in the main on the operation of natural 

 causes. 



Prof. H. H. SwiNNERTON. — The marshland of east Lincolnshire. 



The Lincolnshire marshland is the northerly continuation of the Fenland. 

 As its coastal margin is undergoing marine erosion many natural exposures 

 of the underlying deposits are available. These show that the general 

 history of the area is one of recurrent alteration in the relative level of land 

 and sea, accompanied by the laying down of alternating deposits of estuarine 

 clays and fen peats. The youngest deposits consist of silty clay containing 

 cockles, oysters and Scrobicularia, which show that it was laid down in the 

 low tide zone. This clay rests upon a surface well defined by a thin peat, 

 the presence of a Roman site and the debris of many early Iron Age salt- 

 workings. These facts suggest a stationary condition for the area from the 

 close of the Bronze Age to the last century of the Roman occupation, fol- 

 lowed by a rapid subsidence of nearly 20 feet. Underlying this surface the 

 following deposits occur from above downwards : thin freshwater clay ; 

 8 feet of marine silts, crowded with the remains of salt marsh plants ; and 

 2 feet of peats, enclosing the ruins of a forest. The last named have yielded 

 one implement of neolithic type, and the composition of the peat points 

 to the climatic conditions of the latter part of the Atlantic Period. The clays 

 with salt marsh plants thus represent a subsidence, during the Bronze Age, 

 which took place so slowly that the area was always situated within the limits 

 of the high tide zone. 



Afternoon. 

 Excursion to Barnwell, Cherryhinton, and Barrington. 



Friday, August 19. 



Discussion on The distribution and migration of certain animal groups in 

 the British Lower Palceozoic Fauna (lo.o). 



Dr. C. J. Stubblefield. — i. The Trilobites. 



' Larval ' trilobites were presumably planktonic, adults neritic or nektonic. 

 Some genera are more usually found in mudstones, others in calcareous or 

 sandy deposits, many are independent of facies ; trilobites are notably 

 absent from truly planktonic deposits — radiolarian cherts, graptolite shales 

 (s.s.). The geographical affinities, changes and distribution of successive 

 faunas are discussed. The contrast between the faunas of the Scots-Irish 

 area and the Anglo-Welsh area persists from Lower Cambrian to Balclatchie 

 times with possible intermigration in the south about the time of Nema- 

 graptus gracilis. These Scots-Irish faunas have affinities with the Appalachian 

 and Baltic regions. In Arenig times, in the Anglo-Welsh area the earlier 

 faunal affinity with Scandinavia is lost ; new genera appear in South Wales ; 

 the arenaceous Synhomalonotid fauna spreads to North Wales and Shrop- 

 shire but the Cyclopygid-Trinucleid fauna also reaches the Lake District. 

 Llanvirn faunas of South Wales and Shropshire have Bohemian relation- 

 ships ; Llandeilo, and early Caradoc of East Shropshire also show southern 



