314 A. J. JUKES-BROWNE ON - THE RE1ATIONS OF 



Fig. 9. Corbis gcmltina, Pict. Phosphate cast. 



10, 12. Lucina tenera, Sow. Cast from the Cambridge phosphate-bed. 

 11. . Specimen from Gault of Folkestone, with shell, for 



comparison. 

 13. Cidaris gaultina, Forbes. A fine cast in phosphate, retaining portions 



of the test. (Two thirds nat. size.) 

 14. . Segment of test, from which only one plate is missing : from 



the Gault of Folkestone, in the collection of Mr. F. G. H. Price, F.G.S. 

 15, 16. Pseudodiadema Oarteri, Woodw. Fig. 16 shows segment of same 



enlarged. 

 17. . One of the original specimens in Mr. J. Carter's collection. 



Discussion. 



Mr. Chaeleswoeth considered that the vexed question of the true 

 relations of the so-called Upper Greensand of Cambridge had been 

 now determined, and that it must be regarded as Gault. The presence 

 of Endogenites erosa and other Wealden forms in the deposit at Potton 

 in Bedfordshire, would seem to show that it belonged to the Wealden ; 

 while the presence of Kimmeridge species might be taken to prove 

 that it was Kimmeridge. "With regard to the so-called coprolites, 

 he remarked that it was difficult to assign those of the Red Crag, as 

 well as those of Cambridge, to their true position. He inquired 

 how did the phosphatic nodules originate ? Some observers maintain 

 that they are rolled ; but in the Crag the shark's teeth have nodules 

 attached to their base, and these could not have been acted upon by 

 erosion. He thought the phosphates were derived either from de- 

 composed marine vegetation or from excrements. 



Mr. Peice corroborated all. Mr. Jukes-Browne had said, and 

 remarked that he observed in the collection of the so-called Upper 

 Greensand fossils in the "Woodwardian Museum at Cambridge a 

 large preponderance of forms which he could assign as belonging to 

 the Gault. In that collection he counted as many as 75 species 

 which he recognized as being similar to those found at Folkestone, 

 63 of which were common to the Upper Gault, and 12 to the Lower 

 Gault. The whole collection at Cambridge shows as much as 30 per 

 cent, of Gault forms. In the Greensand seam which traverses the 

 Upper Gault at Folkestone, nodules and fossils occur which are 

 identical both as regards species and mineral characters with those 

 from the Cambridge area. The beds denuded in that basin represent 

 X. and XI. of the Folkestone Gault, and part of bed IX., as proved 

 by the presence of Inoceramus sulcatus at Cambridge. 



Prof. Seelet remarked that when he commenced the study of the 

 question discussed in Mr. Jukes-Browne's paper, the fossils of the 

 so-called Cambridge Upper Greensand were very imperfectly known, 

 and the prevalent belief among palaeontologists was that the stratum 

 represented the Gault. As the collections at Cambridge were accu- 

 mulated, and his acquaintance with English sections of similar de- 

 posits was enlarged, he had enjoyed opportunities of discussing the 

 question with foreign palaeontologists, and now believed that the 

 deposit essentially represented the English Upper Greensand. He 

 had noticed that the surface of the Gault on which the Greensand 

 rests is eroded, the phosphatic nodules being spread uniformly, though 



