Geological Society of London. 383 



mentioned that Baron von Waltershaiisen had presented to the 

 Society photographs of his magnificent original drawings of the 

 whole region of Etna, which were upon the table, of which only 

 three copies were taken on a larger scale than the published maps. 



2. '' On the structure of the Crag-beds of Norfolk and Suffolk, 

 with some observations on their Organic remains. — Part II. The 

 Eed Crag of Suffolk." By Joseph Prestwich, Esq., F.R.S., F.G.S. 



The superposition of the Red Crag to the Coralline having been 

 clearly shown by previous writers, the author confined his paper to 

 those questions on which differences of opinion still exist, namely, 

 the structure of the Red Crag, its affinities with the Coralline, and 

 its exact relation to the Mammaliferous Crag of Norfolk. The Red 

 Crag of Suffolk was described as occupying an excavated area in the 

 Coralline, wrapping round the isolated reefs of the latter, filling up 

 the hollows between them, and occupying a similar, and sometimes 

 a rather lower level than the summits of these older reefs. It forms 

 such an extremely variable series of beds, that the author had been 

 unable to observe any definite order of succession in the greater part 

 of it ; but he remarked that oblique lamination is most strongly 

 developed in the lower and central portions, and that almost every- 

 where there occurs at the base a bed of phosphatic nodules, although 

 deposits of that nature are by no means confined to one level. Old 

 sea-cliffs of Coralline Crag, and remains of old sea -beaches at their 

 base, were described by Mr. Prestwich as occurring at Sutton ; and 

 he also gave detailed descriptions of numerous pits in the Red Crag 

 of Suffolk, where the phenomena which he described may be ob- 

 served. Dividing the Red Crag into an upper, frequently unfossili- 

 ferous, member, the fossils of which, being most frequently in the 

 position in which they lived, may be regarded as truly representing 

 the fauna of the period ; and a lower fossiliferous portion, in which 

 the shells are found mostly in a broken and comminuted state, and 

 mixed largely with fossils derived from the older Coralline Crag ; the 

 author described their distribution in Suffolk, and their mode of oc- 

 currence on the eroded Coralline Crag, referring more especially to 

 the difficulty in drawing the line between them in many cases. 



In treating of the Organic Remains of the Red Crag, Mr. Prest- 

 wich gave lists of the shells found at the different localities, which 

 had been prepared with the aid of Mr. Gwyn Jeffreys. Taking the 

 local conditions into consideration, eliminating the extraneous fossils 

 of the Red Crag of Sutton, Butley, &c., and excluding the freshwater 

 fossils of the more nothern districts, the author regarded the remain- 

 ing fossils of the two divisions of the Red Crag as being so closely 

 related, that the whole group must palseontologically be treated as 

 one. Mr. Searles Wood had given the total number of species of 

 its Mollusca as 239 ; to these Mr. Gwyn Jeffreys has added six 

 additional species; on the other hand, he regarded ninety-nine of 

 them as varieties and extraneous fossils, leaving 146 species be- 

 longing to the Red Crag. Of these Mr. Jeffreys has identified 133, 

 or 92 per cent., with living species, 115 still being inhabitants of 

 British seas, 15 being found in more northern seas, and 3 in more 

 southern. 



