36 THE ' DERIVED ' FOSSILS. 



much penetrated by lithophagous mollusca. Altogether the 

 pebbles are very similar to those of the Upware Neocomians. 



Terebratula ovoides, Sby., and other fossils, were found by Mr 

 Seeley. 



Thus in all these localities extending from S. Willingham in 

 Lincolnshire to Cambridge and Suffolk we have a set of similar 

 rock boulders containing Terebratula ovoides and T. rex. But the 

 Herrimere mass is of particular interest, because besides the Tere- 

 bratula it contains a number of other species which serve to fix the 

 geological age of the original deposit. These are, Belemnites, sp. ; 

 Terebratula ovoides (Sby.); *Cucullcea errans (Keeping); *Pecten 

 striato-costatus (Roemcr); *Pecten orbicularis (Sby.); * Li ma long a 

 (Roem.)?; Pholadomya; Lucina (same species as at W. Dereham) ; 

 Trigonia (Mr Ray Lankester) ; *Exogyra Tombeckiana (d'Orb.) ; 

 *Avicula macroptera? (umbo large, ribs stout and rounded). 



In the notice of this rock in the Geological Magazine above 

 referred to the importance of its fossils, as helping to settle the age 

 of the grit boulders, was fully recognised, but I cannot find any 

 proof that the rock occurs "in situ beneath the bed of the Cam," 

 as there stated on the authority of Mr Seeley; nor can I admit 

 that the fossils "agree with the stratigraphical position of the bed 

 as the very highest of the oolites." Notwithstanding the long- 

 continued work of dredging in the bed of the Cam, the rock has, I 

 believe, never presented itself but on this one occasion, and as to 

 its stratigraphical position a glance at the map will show that it 

 lies between the coral rag of Upware and the Kimmeridge clay of 

 Ely. Again, its fossils, such of them as give any evidence at all, 

 point to the Neocomian age. Six of the species are, I believe, 

 cretaceous, namely, those marked with an asterisk in the list. 



Now of the Herrimere boulder fossils the two most special and 

 characteristic species also occur as derived fossils in the Upware 

 coprolite bed, namely Terebratula ovoides, and the Cucullcea emans 

 of the dark grit; and the latter species is unknown in any other 

 rock. I believe therefore that both sets of boulders, those now 

 imbedded in the lower greensand of Upware and those scattered 

 about the country in gravels and surface drift, were all derived 

 from the same parent rock. 



Other links in the chain of evidence are afforded by the 

 second species of Cucullcea, C. Donningtonensis n. sp. and the 



