72 ME. G. W. LAMPLrGH OX THE jrXCTIO^' OF [vol. Ixxviii, 



showed that the Gaiilt forms were proper to the hed and that the 

 clay was stratigraphically distinct from the Chalk Marl. The 

 bearing of tliis discussion on the present case is close, not only by 

 reason of the stratigraphical horizons involved, but also because 

 most of the fossils dealt with in the argument are species found 

 at Shenley, and now again brought into question : such as — 

 ' Inoceramus concentricus ' with ' crippsi ' and allies, ' Ostrea 

 vesicularis,' ' Belemnites minimus' and vars., etc. 



The limestone fauna. — The argument for the ' Ceno- 

 manian ' age of the limestone is not based on a consideration of 

 the fauna as a whole, but on certain species the occurrence of 

 Avhich is supposed to be impossible below the Gault ; other species, 

 to be regarded as neutral, are not discussed ; and those which tell 

 distinctly against the hypothesis, if mentioned at all, are considered 

 ' without doubt ' to be derivative. I think that it will brinsr the 

 matter into better j)erspective if I summarize the evidence in each 

 Class, and add particular comments on the species which have 

 been used in the argument as they come under review. 



Cephalopoda. — Of the ammonites (six specimens in all), those recogniz- 

 able belong to two forms proper to the Mammillatus Zone and not known to 

 occur above it. The evidence against the supposed derivative origin of the 

 identified specimens has been already stated (p. 47). The belemnites (two 

 specimens) are probably a form of Neohiholites occurring in the same zone 

 (p. 47). 



Gastropoda (see p. 47). — No specific identifications have been made, and 

 no argument raised. The assemblage will probably be found to present a 

 ' Lower Gault ' facies, and to have its equivalents among the rich fauna of 

 this Class recorded from the Mammillatus Beds of Northern France.^ If there 

 had been any recognizable ' Cenomanian ' forms among them, I think that they 

 would have been mentioned in the discussion. 



Lame LLiBKANCHi ATA (see p. 47). — Only four species received positive 

 determination in our original list (L.W., p. 263), and all are species known 

 to range downwards in the Lower Greensand, at least as low as the Hythe 

 Beds, and upwards into the Chalk. They happen to embrace the commonest 

 fossils of their Class in the limestone. Of the six more or less doubtful 

 determinations in om' original list, three were species not previously known 

 above the Lower Greensand, and the other three were known only in or above 

 the Gault. One of the latter, Lima glohosa, has since become a positive 

 determination, and will be further commented on. 



Of the five or six new determinations (pp. 57-58), Inoceramus concentricus 

 is important in strengthening the relationship of the bed with the overlying 

 clays ; while Pteria pectinata, an abundant fossil at Shenley, has a wide dis- 

 tribution, ranging from the Hythe Beds up into the Chalk, but is commonest 

 in the Lower Greensand.^ These two species are not referred to by Dr. 

 Kitchin & Mr. Pringle, who quote the four following in support of their 

 argument: — 



(i) Pecten curvatus, ' which occurs in the Upper Greensand of Great Haldon 

 and in the Chloritic Marl ' (K.P., p. 5). Eegarding this small pecten, Mr. H. 



^ See list in C. Barrois, ' Terrain Cretace des Ardennes,' Ann. Soc. Geol. 

 Nord, vol. V (1878), pp. 269-75. 



^ H. Woods, ' Monogr. Cretac. Lamellibr.' vol. ii, pt. 2, p. 59, Pal. Soc. 

 1905. 



