Vol. 50.] MR. F. CHAPMAN ON THE BARGATE BEDS OF SURREY. 683 



examined the spicules from this bed and also from that at Littleton , 

 and remarks upon them as follows: — "These beds with sponge- 

 remains are very similar to those in the same formation at Godalming, 

 Haslemere, Sevenoaks, and other places in Kent, Surrey, and Sussex. 

 Thin layers of the rock are mainly composed of detached spicules 

 of various forms, indiscriminately mingled together, and cemented 

 by a siliceous deposit one to the other. The spicules are usually 

 much fractured, and their original opal silica has been changed to 

 chalcedony and quartz. In places they are not cemented together, 

 and they can then be picked out from the sand-grains of the rock. 



" The spicules belong to various forms of sponges. The styliform 

 and pin-shaped forms are like those of the existing monactinelJid 

 genera Axinella and Dirrhopalum (from St. Martha's). The most 

 numerous spicules are the trifid forms of the tetractinellid genus 

 Qeodites, of which at least four species are present, G. robustus, 

 G. obtusus, G. Gaudryi, Fischer, sp. (all from St. Martha's and 

 Littleton), and G. Garleri (from St. Martha's). There are also 

 caltrop spicules of Pachastrella (from St. Martha's and Littleton). 

 The Lithistida are represented by spicules of Mastosia (from St. 

 Martha's), Doryderma (from St. Martha's and Littleton), and 

 lihayadinia (from Littleton). There are likewise fragments of the 

 mesh and nodular masses of a hexactinellid sponge (from Littleton), 

 which has not yet been determined." 



Above this sponge-deposit, and on the west side of the road, is a 

 large exposure of pebbly beds with intercalated clay- seams, con- 

 taining many species of foraminifera and a few ostracoda. 



Higher up the lane Bargate Stone begins to predominate, alter- 

 nating with pebble-beds and calcareous grit. In the siliceous 

 residue of the JBargate Stone from this spot Bulimina obtusa, d'Orb., 

 and Lagena globosa (Mont.), silicified, were found, and also two 

 specimens of a polyzoan, which have been determined by Dr. J. W. 

 Gregory, L.G.S., as a species of ETeteropora. 



The Bargate Stone at this locality is extremely interesting, on 

 account of the occurrence of calcareous oolitic grains and brecciated 

 fragments of oolite in the rock (see fig. 2, p. 684). It seemed at 

 first probable that the oolitic grains might have been formed with 

 the rock in which they are found. Closer examination showed, 

 however, that they had been derived from an older rock, since 

 many exhibited signs of attrition, and had hard abrading particles 

 still adhering to or pressed into them. Moreover, some of the 

 grains were massed together, as they would appear in the original 

 rock ; and further, the quartz and other grains in the rock are 

 perfectly free from calcareous deposit. These grains were evidently 

 derived from a calcareous oolitic rock of loose texture, resembling 

 some of the more friable ' roestones.' Other examples of Bargate 

 Stone were mainly composed of breccia, derived from a compact 

 oolitic limestone. One of the rock-specimens containing the 

 calcareous oolitic grains is of a pale reddish-brown colour, with 

 darker ferruginous streaks and veins ; the weathered surface of the 

 rock shows the oolitic grains quite distinctly. The rock is always 



