318 A. J. Jukes-Broivne — On the term Neocomian. 



all authorities to be homotaxial with the Hauterivien marls and 

 Spatangus limestones, and the oldest Neocomian rocks which under- 

 lie these are not therefore represented in the Yorkshire area. I see 

 no reason however why the zone of Am. noricus should be excluded 

 from the Neocomian, since that Ammonite is probably only a variety 

 of Am. neocomiensis. 



Coming now to the question of general nomenclature, I cannot 

 but think that Prof. Judd's proposal to apply the name Neocomian 

 to the whole Lower Cretaceous series was a very unfortunate one. 

 It would appear that at the time of writing his paper on the Speeton 

 Clay, Prof. Judd was under the impression that this series had a 

 claim to be regarded as a distinct system, both on stratigrapbical 

 and palaeontological grounds; 1 now if subsequent investigation had 

 confirmed this belief, and had led to the establishment of a Neocomian 

 system distinct from the Cretaceous system, but of equal palseonto- 

 logical importance with the other systems which are recognized 

 in geology, no objection could now be taken. But this is not the 

 case : the thickness of the Neocomien, Urgonien, and Aptien rocks 

 in the south of France appears to be very great (from 1000 to 6000 

 feet), but the mere thickness of a group of strata does not justify 

 the creation of a new system unless they contain a sufficiently 

 distinct assemblage of fossils, and in this case the fauna is neither so 

 large and varied or so peculiar as to entitle them to be separated from 

 the Cretaceous system : they are regarded by all who have studied 

 them as forming the lower portion of this system, just as the Gault 

 and Chalk form the upper portion of it, and their separation would 

 be no more justifiable than that of the Lias from the Jurassic system.. 



This being so, the proposal to call the lower series Neocomian 

 ceases to be logically defensible, unless a new name is found either 

 for the Upper Cretaceous series or for the whole system which 

 includes both. Prof. Judd's nomenclature, with the belief he then 

 entertained, was a logical one, but I must maintain that the manner 

 in which it has been subsequently employed is entirely illogical. 

 There is an inclination in certain quarters to adopt the name 

 Neocomian for the lower division, and to limit the application 

 of Cretaceous to the upper division ; this plan would certainly 

 secure logical uniformity, but those who suggest it are bound to 

 propose a new name for the system which includes these two 

 divisions, otherwise it would only "make confusion worse con- 

 founded." There is really no necessity for any such innovation, 

 or for any alteration of the general scheme of nomenclature to 

 which we are accustomed. The Cambrian and the Carboniferous 

 systems are simply divided into lower and upper series, why 

 therefore should we not be content to treat the Cretaceous system 

 in the same way, and to speak simply of Lower and Upper Cre- 

 taceous series ? 



Further, it must be remembered that the majority of French and 

 Swiss geologists use the term Neocomian in its special application as 

 limited by D'Orbigny, and its employment in any other sense, except 



1 See Quart. Journ. Geol. Soc. vol. xxiv. p. 228. 



