4 SUPPLEMENT TO THE CRAG MOLLUSCA. 



The specimen figured in Supplement, Tab. I, was found by Mr. A. Bell at Thorpe, 

 in Suffolk, and in the ' Crag Moll.,' vol. i, Tab. I, figs. 14 and 15, are represented some 

 specimens from the Red Crag of Sutton, which are there called Conovulus myosotis (with 

 a doubt). These, I think, may be united with the shell figured in Supplement, Tab. I, 

 although they have no denticles on the inside of the outer lip. A similar, but smaller, 

 specimen has been found at Thorpe, in Suffolk, by Mr. E. Cavell, in which the 

 outer lip has also indications of denticles. This shell is much larger and more fusiform than 

 the existing myosotis, has a more pointed base, and is a thicker shell. 



Mr. Bell, in the ' Geol. Mag.,' vol. vi, p. 41, gives Limncea pereyra and L. truncalula 

 as species from the Red Crag of Butley. I have also found Planorbis complanatus and 

 PL spirorbis at the same locality. 



These two or three fresh-water shells thus occurring in the Red Crag do not appear 

 to me to indicate estuarine conditions, as they may have been introduced into the Red 

 Crag sea down those rills of fresh water that we see on every beach between tide marks, 

 coming from the land and meandering over the shore to the brink of the waves. The 

 principal part of the Red Crag, including the Crag at Butley, from which these shells were 

 obtained, being a beach or foreshore deposit, i. e. one formed between high and low 

 water marks, land and fresh- water shells so carried down would become incorporated with 

 the purely marine deposit, and thus impart a different aspect to a formation from that of 

 a fluvio-marine one, which is produced by the gradual intermingling in an estuary of a 

 fresh-water river with the salt water of the sea. It is clear from the position of the Red 

 Crag at Butley relatively to the Coralline Rock bank against which it abuts, that the shore 

 was immediately contiguous to the places from which these fresh- water shells were derived. 

 Even those parts of the Red Crag which appear to have been formed actually under water, 

 such as that under which the phosphatic nodules are worked, were in the immediate 

 contiguity of the foreshore deposits with which they are associated, and may easily have 

 received introductions of land and fresh-water shells in a similar way. 



PECTINIBRANCHTATA. 



Marine. 

 Ovula Leathesii, Sowerby. Crag Moll., vol. i, p. 14, Tab. II, fig. 1, a, b. 



Localities. Cor. Crag, Sutton and near Orford. Red Crag, Walton Naze and Butley. 



Two varieties of this Crag fossil were figured as above referred to, both of which were 

 considered there as referable to Bulla spelta, Linne. 



At fig. 23, Tab. VII, of this Supplement I have given a front view of the short variety, 

 the back of which was represented in ' Crag Moll.,' Tab. II, fig. 1, b, from the Red Crag. 



