590 MESSES. GAEDXER, KEEPITS^Gr, AND MONCKTOIf 0]^ THE 



specimens of the strictly Barton fossils, Voluta luctatrix, Crassatella 

 sulcata^ and Limopsis scalaris, are obtained here, -while others, such 

 as Voluta ainhigua and Pleurotoma rostrata, cannot be collected 

 at all above this zone. Finally, several small but well-known 

 species, such as Conus dormitor and Buccinum desertum, make their 

 first appearance here. 



The XJppee Baetons, oe Chama and Becton-Bunny Beds. 



Between the shell-bed with Tellina amhigua and T. Branderi 



and the C7iama-bed, there are a few feet of buff sandy clay, breaking 

 up into cubes from 3 to 9 inches square, which are full of a peculiar 

 variety of Turritella. It is in this bed that Scalana acuta, Fusus 

 turgidus, and Voluta suhamhigua are found. 



The Chama-hedi is a mass of steel-grey (commonly called blue) sand, 

 with a slight mixture of clay, the proportion of the latter decreasing 

 upwards. Mr. Grenville Cole describes it as angular and sometimes 

 very minute sand, with much fine brown mud and a few green 

 grains. It forms almost a running sand in the chff, at a very low 

 angle, and is therefore invariably buried under masses of gravel and 

 mud fallen from above, and exceedingly difficult to measure. Dr. 

 AYright found it to be from 10' to 15 feet thick, and Prestwich esti- 

 mated it at 20 feet. Though we failed to obtain any measurement 

 at first, we subsequently found the base resting on the shell-bed in 

 a drain cut under the Coastguard Station, and were able to get a 

 fairly satisfactory measurement, showing a thickness of 18 feet. A 

 perhaps even more accurate measurement was obtained by taking 

 the outcrop along the shore, between the uppermost Septaria-zone 

 and the top of the C7zawia-bed, a distance of 268 yards, at a dip of 

 2J°, when, after making all allowances, the thickness also came out 

 at 18 feet*. 



The beds are unfossiliferous everywhere, unless capped by the 

 stiff clay of the Becton-Bunny Beds, and they dip under the beach 

 somewhere about 100 yards east of the fence dividing the lands of 

 Col. Clinton from the Hinton-Admiral estates. Where fossiliferous, 

 the Chamas occur in extraordinary profusion, especially towards the 

 top, with the valves most frequently united, while Turritellas abound 

 no less towards the base. Chamas are excessively rare in the lower, 

 and none are found in the middle division of the Barton, and this 

 is the iast appearance of the genus in England. Their presence is 

 very remarkable, and suggestive of a change in the physical condi- 

 tion of the sea-bed, for they inhabit tropical seas, especially among 

 coral reefs. Many interesting and beautiful shells make their first, 

 or almost first, appearance in the 7 or 8 feet of clayey sand at the 

 base of this bed, such as TypMs JistuJosiis, Conus scahriculus, Voluta 

 costata, V. Jiumerosa, Miu^ex defossus, Mitra scahra, Trochus nodu- 

 Josus, and Cyprc^a hartonensis. Above these we find TereheUmn 

 sopitum and Vidsella. Still higher, in the more sandy bed, among 



* 268 yds. at 2i°=35'-15', of Middle Barton =20' -2', difference of level at 

 .the two extremities=18'. 



