A. 8f B. Bell— On the English Crags. 259 



to the Walton-on-tlie-Naze shells, as we shall show presently ; and 

 we may mention that our Walton list of shells enumerates 170 

 species, 116 of them being common to the Coralline Crag. Speaking 

 of some forms from a particular stage, he remarks, they are " worn 

 and travelled, and show their origin to have been mainly derived 

 from older materials." Sir Charles Lyell also dwells upon the 

 subject in his Students' Elements, p. 17^. He says, "There can 

 be no doubt Conchologists have occasionally rejected from the Eed 

 and Norwich Crags shells which really belong to the seas of those 

 periods because they were extinct, or unknown as living," and 

 suggests that extreme scarcity, colour, and worn condition may 

 sometimes be indicative of derivative origin. 



An analysis of the quotations just made will therefore give the 

 following as marks of extraneous origin : — Separation of bivalves, 

 damaged univalves, mixed without regard to position, and mostly, 

 if not always, in bad and worn condition. Extreme scarcity and 

 colour, or want of it, being dependent upon local consideration, do 

 not bear upon our argument. 



These characters are not universally applicable to the members of 

 the Eed Crag fauna ; thus, we find bivalves in pairs and in situ every- 

 where, of course more abundantly in some places than in others, and 

 we have prepared a list of upwards of fifty species. These species are 

 many of them of the most delicate structure, especially as regards the 

 ligamental apparatus. The Brachiopoda, and species of Hinnites, 

 Pecten, Astarte, Cardium, Solen, Mya, TelUna, Mactra, and Pholas 

 constantly occur in pairs. Of Terebratula grandi^, var., we have 

 seen upwards of 500 examples, perfect in many cases, even to the 

 preservation of the internal apparatus. Perhaps the most striking 

 proof of the non -derivation of the Brachiopoda is furnished by their 

 situation in the Crag. They occur in groups imbedded in fine sand, 

 and are almost always surrounding large round stones, and only 

 want the connecting pedicles to make the group complete. Of the 

 univalves the following forms. Valuta, Mitra, Py/rula, Cancellaria, 

 Ovula, Scalaria, Fusus with perfect apices, Eniarginula, Scaphander 

 and various others equally fragile, or highly sculptured, occur 

 in fine preservation. 



Even if this were not so, the arguments derived from worn speci- 

 mens are equally illusory. All naturalists are aware that the pro- 

 portion of worn and imperfect, as compared to perfect specimens, 

 is generally large in dredgings taken below low-water mark, 

 especially if the shells are in. the condition technically known as 

 " dead." 



The worn and decorticated appearance of many of the Crag shells, 

 in our opinion, is owing more to the nature of the investing matrix 

 than to anything else. 



Again, we find in many places traces of an undisturbed sea-bottom 

 determinable by the position and condition of the animal remains. 

 If the bottom of a recent sea was laid dry, we might expect to find, 

 according to local conditions, Terebratidce and Blnjnchonellce. in groups, 

 larger or smaller ; Gastranoe and Myce imbedded in sandy mud and 



