OBSERVATIONS. 17 



Cardium pinnatulum, Con. (nodosulum). Tellina obliqua, /. Sow. (a fragment only 

 Astarte Galeotii, Nyst. by Mr. Bell, another fragment 



Forbesii, S. Wood. by Mr. Hy. Norton of Norwich, 



Circe minima, Mont. and a single valve by Mr. 



Abra prismatica, Mont. Greenhill.) 



Mactra glauca, Born. Mya arenaria, Linn. 



The contrast thus shown by the Crag of Felixstowe to that at Walton Naze (seven miles 

 distant from it) is very striking. At the former place such species as Tropkon costifer, 

 and Nassa reticosa, among Gasteropods, which abound at Walton, and are there 

 preserved in the most perfect condition, are, though abundant, scarcely to be found 

 unmutilated ; and such very few examples of them as do occur but little broken are all 

 more or less worn. Among the Bivalvia one of the most abundant shells at Walton, 

 Artemis lentiformis, and which at that place is almost always perfect (though generally with 

 valves detached), is, though very abundant, invariably in fragments at Felixstowe. That 

 this fragmentary condition at Felixstowe can only arise from the presence of the shell in 

 the Crag there being due to derivation from the destruction of anterior accumulations, 

 is shown by the fact that while A. lentiformis, which is thus in fragments is a strong shell, 

 the thin and fragile shell, Tellina pratenuis (a species unknown from the Walton bed but 

 in tolerable abundance at Felixstowe) occurs almost always perfect. It is, in my opinion, 

 abundantly clear that during the time which elapsed between the accumulation of the 

 Walton beds of Red Crag and their destruction and re-accumulation to form the Red 

 Crag of Felixstowe, such shells as TropJion costifer, Nassa reticosa, and Artemis lenti- 

 formis, as well perhaps as some others had ceased to live in the Red Crag sea ; and that 

 other shells such as the dextral form of Trophon antiquus, Leda ollongoides, Tellina 

 prcetenms> to which might have been added Nucula Cobboldia, but for the solitary and 

 somewhat uncertain occurrence mentioned in the footnote on p. 16, (all of these 

 being species which endured into the early Glacial sea,) and probably some others 

 which might be mentioned, had been introduced into it. Moreover, the extremely 

 profuse shell of all the rest of the Red Crag and of the Lower Glacial sands, Tellina 

 obliqua, but which had lived in the Coralline Crag sea, was during the Walton accumu- 

 lation so scarce in the Red Crag sea that only a single valve of it and two fragments (by 

 three separate collectors) have been detected there. 



In the Red Crag of Butley the change becomes further marked, both by the greater 

 frequency of these later introductions, and by the presence of arctic species, which have 

 not yet been detected in the Crag of Essex or of the more southern part of Suffolk, the 

 Upper Beds of the Red Crag having either been removed from, or else having never been 

 formed in, that part of Suffolk. 



The changes which led to the peculiar and exceptionally perplexing features thus 

 presented by the beds of the Red Crag of England, with their large admixture of false 



3 



