78 MR. G. W. LAMPLTJGH OX THE JFJSTCTIO]!^ OP [vol. Ixxviii, 



evolutionary character shown by the valves from Shenley Hill indicate a 

 later geological age ' [than the Gault]. The two species identified have a 

 long range in the Gault, as well as later ; and there may well be in this case 

 some misapprehension of the supposed evolutionary characters. 



The Gault fauna. — The palseontological argument about the 

 Grault centres around two pomts : — 



(i) The supposed inversion of the clays under Shenley Hill ; and (ii) the 

 supposed overlap of the Lower by the Upper Gaxilt in other sections. 



On both points the evidence brought forward by Dr. Kitchin & 

 Mr. Pringle in their paper is singularly weak. 



(i) To support their statement that the dark lower clays of the 

 Harris's-pit section (fig. 3) are newer than the overlying pale cla^^s, 

 they depend upon three fossils of the lower beds (K.P., p. 13) : — 

 an Inoceramus ' suggestive of I. crippsi ' ; * small impressions of 

 the characteristically ornamented Nautilus deslongchampsiamis 

 d'Orbigny ' ; and the com^Dressed ammonite ol the ' auritus '-stock 

 identified as Hoplites catillus (see antea^ pp. 51-52). 



The Inoceramus I have already discussed; it is not the form 

 defined as 1. crippsi by Mr. H. Woods in his recent monograph. i 

 although it has sometimes carried that name, but is a form 

 common in the lower part of the Gault {antea, j). 51). The 

 Nautilus may or may not be correctly identified ; it is a small 

 crushed impression, without shape, and hardly comparable with 

 the figured type ; and the species has not (so far as I am aware) 

 been previously recorded from any part of the Gault clays in 

 jGno^land. 



The weight of the argument has apparently to rest mainly upon 

 the crushed ammonite, and it is unfortunate that the species should 

 be one of considerable difficulty. It is discussed at some length by 

 E. T. Newton & A. J. Jukes-Browne in the ' Palseontological 

 Appendix ' to the ' Gault & Upper Greensand ' memoir {op. cit. 

 pp. 413-45), who note, among other points, that 'the flatness 

 exhibited by so many specimens is evidently in most cases due to 

 compression after embedment, and is not an original character.' 

 Jukes-Browne confined his determination to a form occurring in 

 the Upper Greensand, and did not recognize the species as occurring 

 in the Gault clays {op. cit. p. 458). Dr. Kitchin & Mr. Pringle 

 identify their crushed Shenley specimens with the Upper Greensand 

 form, and conclude that * they are members of an easily recognizable 

 hoplitid group which have reached an evolutionary stage char- 

 acterized by degeneration of the sculptural features.' But the 

 characters requisite in the specific determination are precisely those 

 most likely to be simulated in specimens compressed to the condition 

 of ' films on the bedding-surfaces,' as the Shenley examples are. 

 The questionable Shenley ammonite belongs to a sub-genus ranging 



^ 'Monogr. Brit. Cretaceous Lamellibranchia ' vol. ii, pt. 7, pp. 273-78, 

 Pal. Soc. 1911. 



