Vol. 50.] ME. F. CHAPMAN ON THE BARGATE BEDS OF SURREY. 681 ) 



spicules, which, have been preserved in green chalcedony, generally 

 resembling the examples figured by Dr. Hinde. 1 



Among the casts of organisms preserved in green chalcedonic silica 

 are numerous pale-green threads, sinuous, branched, or bent, which 

 may be referred to the parasitic borings of minute plants in the 

 shell-fragments, etc. The perforations appear to have been filled 

 in with the chalcedony, the subsequent solution of the shell setting 

 free the delicate casts of the tubes. From the siliceous residue have 

 been obtained several fragments of shells which have themselves 

 been silicified, and, having lost their inner layer of shell-substance, 

 expose the interlacing filamentous casts still in place within the shell. 



There are also some peculiar fasciculate and divergent masses of 

 pale green chalcedony, composed of cylindrical rods connected by 

 short bars or stolons. These objects are probably casts of polyzoa 

 (see, PI. XXXIII. fig. 11). 



One of the more remarkable specimens from the residue is what 

 appears to be a portion of a calcareous alga allied to the Corallines 

 (see PI. XXXIII. fig. 9). It consists of three joints, each shorter 

 and more circular in section than in Corallina officinalis, but very 

 near that form. I submitted this specimen, with others of a more 

 doubtful nature and somewhat resembling the external form of 

 Lithothamnion (see PI. XXXIII. fig. 8), to Graf zu Solms-Laubach 

 of Strasburg, who remarks that " it is scarcely possible to be 

 absolutely certain of their affinities beyond placing these fragile 

 fossils, at the best, in the Algae -group. However, I hold it very 

 probable that no. 4 represents a Corallina. The form of the joints 

 and the intermediate pieces agrees with it perfectly. No. 1 may 

 well be one of the Diploporai" (see PI. XXXIII. fig. 10). 



The arenaceous foraminifera in the residue are Haplophragmium 

 ema datum, Brady ; H. nonioninoides, Reuss ; H. depress am, Jones ; 

 H. Humholdti, Beuss; H. irregulare (Rom.); Bulimina polystroplia, 

 Beuss; B. obliqua, d'Orbigny; and B.pyrula, d'Orbigny. 



III. The Bargate Beds below St. Martha's Chapel (Chilworth). 



The Bargate Stone and Pebble-beds are seen in, perhaps, greater 

 lithological variation (though not showing so great a development 

 as westward and southward) in the lane leading to Great Halfpenny 

 Farm, on the west side of St. Martha's Hill (Chilworth), than in any 

 other locality. The following are roughly approximate measure 

 ments of the beds exposed in this lane : — 



' Pebbly sand, underlying Folkestone Beds.^j ft., in. 



Bargate Limestone (much of it is oolitic), j 

 Pebbly beds, with clay - seams. (The \ 15 

 foraminifera were obtained from this ' 



bed.) J 



Soft sponge-bed, resting on hard sponge- 

 bed. (Just above the Farm.) 8 



(Ej Pebbly bed, resting on Hythe Sand with 



ironstone 12 



1 Phil. Trans. Eoy. Soc. vol. clxxvi. (1885) pt. ii. pi. xlv. figs. 15a-«. 



