154 Brodie—PJwspliatic Nodule&. 



less phospliatic. Some of the fossils, which all, in a greater or less 

 degree, seem to have been either enveloped in, or permeated by, 

 the phosphatic matter, have been so much water- worn, that it is almost 

 impossible to distinguish them. There are numerous small shells, 

 viz., casts of Terebratidce, Cardlum, broken Plioladomyce, other species 

 of Ammonites too imperfect and eroded to be determined; large 

 Bufonitic palate [Cyclodus gigas), similar to a species which occurs in 

 the Lower Green-sand at Farringdon ; ^ Ichthyodorulites ; bones and 

 teeth of Saurians, much broken and worn, consisting of vertebrae, 

 paddle-bones, dermal scutes, a small femur, and large reptilian 

 teeth, many of which may have belonged to the Pliosaurus. I also 

 picked up part of an oyster, probably 0. deltoidea. 



Every organism in this phosphatic bed is evidently extraneous, 

 and jDrobably was derived from the destruction of the Oxford and 

 Kimmeridge clays, and intervening Coral Eag, from which the 

 phosphatic matter must have been obtained, while the Lower Green- 

 sand was in process of formation. It is well known that similar 

 masses of phosphate of lime occur both in the Gault and Upper 

 Green-sand, though, in both these cases, it does not appear to have 

 been derivative, but to have been deposited on the spot. Although 

 phosphate of lime is known as a simple element in rocks, it is, I 

 believe, generally only present in very small quantities, and in most 

 cases, it must have been derived notably from animals, especially 

 Saurians and fish in all such marine deposits. I am aware that 

 Mr. Seeley is of opinion that the phosphatic masses in the Upper 

 Green-sand, at Cambridge and elsewhere, were derived from Zostera 

 and other marine plants ; but, as in the Lower Green-sand at Sandy, 

 there is such a large preponderance of animal remains, it seems most 

 probable that in that case, and others like it, the phosphates were 

 purely of animal origin. It need hardly be observed that the dis- 

 covery of these phosphates has gi'eatly increased the value of the land, 

 and it now lets at a much higher price, and though, of course, not 

 inexhaustible, are possibly spread over a much larger area than the 

 one at present opened up. The same process is employed in 

 extracting the phosphate and preparing it for agricultural purposes 

 as that used in the Upper Green-sand. 



Mr. Peel has kindly favoured me with the following analysis of 

 some of the best average samples of phosphatic or coprolitic nodules 



made by Dr. Voelcker : Average samples washed Copro- 



of Siftings from lites from 



layers at 1 & 2ft. another spot. 



Water of Combination 5.17 5.67 



Phosphoric Acid * 22.39 15.12 



Lime 32.73 26.69 



Magnesia, Alumina, and Flourine (by difference)... 6.64 4.51 



Carbonic Acid t 3.06 2.18 



Oxide of Iron 8.08 20.61 



Siliceous Matter 21.93 25.22 



100.00 100.00 



* Equalto Tribasic Phosphate of Lime (Bone Earth) 48.51 32.76 



t Equal to Carbonate of Lime. 6.95 4,95 



* The Farringdon Lower Green-sand contains many fossils, derived from the 

 Kimmeridge clay. 



