1866.] WOOD KED CllAG. 541 



the break, if break there be, as anything more than the laying dry 

 for a short period of the shoal-deposit of the Scrobicularia-crag prior 

 to the overspread of the sand, and I now adopt the view expressed 

 by my son that the horizontal Crag which rests on the oblicjue at 

 Chillesford, ''and underlies the Chillesford beds, and which has 

 always, and I think rightly, been regarded as part (although it be 

 the uppermost part) of the Red Crag, is newer than the true 

 Norwich or Fluviomarine Crag of Thorpe and Wangford. 



The palaeontological aspects presented by the Eed Crag, however, 

 are the principal objects to which I desire to call attention, as 

 affording evidence of one of the most rapid changes in a fauna, when 

 measured by the vertical thickness of the beds furnishing it, that 

 geology affords ; and as the most convenient and concise way of 

 representing the beds between the base of the Crag and the Boulder- 

 clay, to the lower portion of which my observations refer, my son 

 has prepared the annexed diagram, with a list of the various sections 

 from which it results, embodying the succession and relationof these 

 various beds according to his latest researches (see pp. 548, 549). 



In the case of the Coralline Crag, we have evidence that it contains 

 the exuviae of animals the most removed from our own marine fauna, 

 in the fact that in it are the remains of 27 genera that are extinct 

 in the British seas : — 



^tCultellus. Nucinella. *Pleurotoma. 



*Panop8ea. Hinnites. Cassidaria. 



Pholadomya. Lingula. Terebra. 



Coralliophaga. Orbicula. ifColumbella, 



Chama. Sigaretus. Triton. 



■sfrCardita, ^Pyramidella. Pjrula. 



Verticordia. Fossarus. ^Voluta. 



Erycinella. ^Cancellaria. Ditrupa. 



ifScintilla. ieEingicula. Cleodora. 



The genera marked with an asterisk are represented at Walton-on-the-Nazc. 



From this it is fair to infer that this Crag belonged to a period long 

 antecedent to the deposition of the Eed. Indeed so far as the word 

 " Crag" indicates any material affinity between the two formations 

 it misleads, since, remote as it is, and severed from the present time 

 by a considerable sequence of deposits and events, the oldest part of 

 the Red Crag is less removed, palaeontologically, from the present 

 time (and far less so from the Chillesford beds) than it is from the 

 Coralline Crag thus associated with it in name, but dissociated from 

 it in fact. The Red Crag, on the other hand, contains within itself 

 the evidence of a transition by stages, from the oldest, where its affi- 

 nities were to some extent with the coralline, and in a greater extent 

 with the existing Mediterranean, to its newer stages, in which the 

 shells are very few and confined to types peculiarly northern . Of these 

 stages the oldest and best-marked is that of Walton-on-the-j^aze : 

 this Crag contains a fauna presenting a facies strongly indicative of 

 an origin or connexion with more temperate seas ; and although there 

 is an absence from this bed of not less than 17 of those 27 genera 

 before mentioned as belonging to the Coralline Crag (a few of which 

 may perhaps be due to difference in depth of deposition), still the 



