xii SUPPLEMENT TO THE CRAG MOLLUSCA. 



The limits of the Chillesford clay were extensive, for we find what seems to be this 

 deposit as far north-west as Needham Market, 1 showing that the valley of the Gipping had 

 come into existence prior to the Crag period ; while well-preserved remnants of it extend 

 northwards to near Burgh and Oxnead, on the Bure, and to Barton Turf on the Ant. 



The Mammalian Remains of the Crag. 



Before leaving the subject of the Upper Crag, the bed of rough flints which occurs, not 

 only at the base of the Fluvio-marine Crag, but also at that of the Chillesford sands, 

 where these rest on the Chalk, should be noticed. The mammalian remains (chiefly molar 

 teeth) which have come from this bed have been regarded by some as belonging to the 

 fauna of the Upper Crag period ; while by others this bed is regarded as an old land 

 surface, in which the remains of animals that lived upon it are imbedded. From both 

 these views, however, we dissent. Land surfaces are not to be looked for in a bed of 

 rough flints, without any traces of a peat or soil covering, but in such beds as those of 

 the forest series presently to be described ; while it is not in pure land surfaces that the 

 remains of the mammalia that lived on it are preserved (for in these the bones perish into 

 dust by atmospheric agencies), but in the sediment of the pools, lakes, swamps, and 

 rivers of the time ; and even in these we find the remains in a more connected form 

 than that of bouldered teeth, and portions of the more solid parts of the bones, such as 

 have come from this bed of rough flints. On the other hand, these are just the remains 

 which, when an anterior deposit yields to cliff waste, escape destruction from the waves, 

 and are preserved in the estuarine and coast deposits of the subsequent period. Ac- 

 cordingly, we believe the origin of all the mammalian remains found in this bed to be 

 derivative equally with the rough flints themselves ; and we may add that marine Mollusca 

 sometimes occur in the bed, though we never heard of a land shell having been found in it. 



"With the exception of the connected cetacean vertebrae which occurred a few years since 

 in the Chillesford clay at Chillesford, it therefore seems to us open to much question whether 

 any of the mammalian remains obtained from the Fluvio-marine Crag, or from the Chillesford 

 beds, belonged to individuals which lived during the accumulation of these deposits. In the 

 case of the Red Crag we venture to affirm that all such remains (even those of the Ziphioid 

 Cetaceans, notwithstanding their occurrence at Antwerp) are derivative ; since, indepen- 

 dently of their consisting only of isolated fragments, more or less bouldered and perforated 

 by lithodomous Mollusca, they do not occur in the body of the Red Crag itself, but only 

 in the nodule bed at its base, which is, par excellence, a bed of erratics of all sorts. Of 

 derivative origin also, are, as it seems to us, the mammalian remains occurring at the base 

 of the Coralline Crag. 



\-v 



1 Iii a pit on the north of the town by the Windmill. One side of the section shows the laminated clay 

 forced up into a vertical position, apparently by the pressure of land ice during the subsequent Glacial period. 

 There is a pit of micaceous sand three furlongs north-west of Easton Church (six miles north of Woodbridge) 

 that may belong to these Chillesford bed3, but we have not ventured to show it as such in the map. 



