Oct. 12, 1882] 



NA TURE 



581 



of abrasion, when the "floor" is covered by the strati- 

 fied sand or mud of the river, the tools are all as sharp as 

 on the day they were made. 



It fortunately happens that very near the sections here 

 illustrated, viz. at 270 yards west by north from Clapton 

 Railway Station, and just south of Caroline Street (marked 

 on Stanford's map), one or two other cuttings have quite 

 recently been made, these show admirable sections of 

 characteristic " trail." At Fig. 3 a section facing south 

 is engraved to scale, and at Fig. 4 the end of the section 



is further enlarged to show the " trail " above and the 

 stratification below. The section is 1 1 feet 6 inches deep, 

 and just reaches the top of the stratum of gravel which 

 contains implements intermediate in age between those 

 of the " floor " above, and those found from 20 feet to 30 

 feet beneath the surface. The " Palaeolithic Floor" on 

 Fig. 4, if present, would be just above the hortozanal 

 bands of stratification, but the " trail " at this spot has 

 swept it away, it however occurs in a perfect state a few 

 yards off. Beginning at the top, the reference-letter. R, 



is humus ; Q, mud belonging to the " trail " ; O, " trail " ; 

 P, a pocket of London Clay ; N, Palaeolithic sand and 

 loam crumpled and disturbed by the " trail " ; M, dark 

 sand and clays ; L, light sand and clay ; k, dark sand 

 and clay ; J, yellow sand ; I, red sand ; H, light sand and 

 clay ; G, dark sand and clay ; F, red sand"; E, yellow 

 sand; D, red sand; c, sand, almost white; B, buff sand, 

 sometimes full of the fossil shells of land and freshwater 

 molluscs. These sands represent the sandy margin of 

 the old Thames, now four miles distant from this spot. 



Some of the shells found in it by me have been kindly 

 named by Dr. J. Gwyn Jeffreys; the series is probably 

 very imperfect, as the time 1 have for geological matters 

 is extremely limited, but no doubt the list is typical, as I 

 have many times met with the species hereafter men- 

 tioned ; other species may be more rare or local. 



1. Corbicula flitminalis, Mull., extremely common. 



2. Hydrobia marginata, Mich., not uncommon. 



3. Spharium contemn, Linn. 



4. Pisidium fmitinale, Drap. ; var. Hensloiuana, Jen. 



a- 77 f : 



i- : :'~:^> ■ /.::;■ V.' : 





y^PY^*"* 



Fig. 4. 



5. P. amniciim, Mull. 



6. Unto tumidus, Phil. 



7. Bythinia tenlaculata, Linn, extremely common, 



with abundant free opercula. 



8. Valvata piscinalis, Miill., var. subcylindrica. 



9. Planorbis albus, Mull. 



10. P. complanatus, Linn. 



11. Limnaa auricularia, Linn. 



12. L. truncatula, Miill. 



13. L.peregra, Miill. 



14. Ancylus fluviatilis, Miill. 



15. Helix concinna, Jefft. 



16. H. nemoralis, Linn. 



Dr. Jeffreys was good enough to add the following 

 note : — " The occurrence of Pisidium fontinale, var. 

 Henshnoana, as well as the tout ensemble of all these 

 fossil shells, induces me to believe that they had been 

 thrown up by floods on the banks of a large river such as 



