PLEISTOCENE GEOLOGY OF THE THAMES VALLEY. 353 



Fishfs fyom the Pleistocene of Grays Thurrock. 



Acerina vulgaris ? Cuvier, 

 Esox lucius, Linn. 

 Leuciscus rutilus, Linn. 



,, vulgaris, Flem. 



,, erythrophthalmus ? Linn. 



Anguilla ? anguilla ? Linn. 



All these fishes are characteristically freshwater species 

 which are living at the present day in the rivers and lakes of 

 England and Europe. 



MOLLUSCA. 



In 1897 ^fter a careful examination of all existent material 

 and a revision of the previously published lists, Mr. B. B. 

 Woodward and one of us were able to list 49 species from the 

 Middle Terrace, but of these no less than 18 were unrepresented 

 in any collection, whilst several other records were rejected for 

 various reasons. Of these rejected species only one has 

 rewarded our researches, viz., Clausilia hiplicata, first recorded 

 by S. V. Wood. There can be but little doubt that the record 

 of Balea perversa is an error, as already suggested by the same 

 writer, for numerous tops of Clausilia have been found. We 

 are now able to verify seven records hitherto unrepresented by 

 extant specimens. The remaining unverified records are left for 

 what they are worth, and of these no less than nine are on the 

 authority of S. V. Wood. This collection is now in the Norwich 

 Museum, and it has been examined by one of us, and these 

 species are not to be found there. They are all known from 

 other Pleistocene deposits so that there is no inherent improba- 

 bility in their occurrence, but we venture to think that no 

 reliance can be placed on them. ' We have found forty-five 

 species, of which ten are new records. There are four species 

 known from Grays which we failed to find, whilst twelve 

 recorded forms are still absent. 



Agriolimax agrestis, Linn. This form is represented b}' 

 numerous examples not only in our collection but also in the 

 Natural History Museum. These latter examples were collected 

 by Mr. Pickering and presented by him to the Geologists 



