14 F. L. Kitcliin and J. Pringle — 



These well-known ammonites have not been adequately studied, 

 and their relationships remain to be ascertained. They are discoid 

 in form, and are characterized by strongly curved ribs and the loss 

 of these ornaments in the later growth-stages, during which, how- 

 ever, traces of the flattened, swollen rib-endings on either side of 

 the smooth, narrow peripheral area continue to be shown. The 

 naming of these distinctive forms is of little importance in the present 

 connexion ; it is sufficient to say that they are members of an easily 

 recognizable hoplitid group which have reached an evolutionary 

 stage characterized by degeneration of the sculptural features. The 

 significant point is that they give us an important datum-line. 

 A specimen of one of them from the Upper Greensand near Devizes 

 has been kindly examined for us by Dr. B. Pope Bartlett, who, 

 after discussing the matter with Mr. J. Scanes, has expressed the 

 opinion that it came from a position about 60 to 80 feet below the 

 base of the Cenomanian stage. This is in the rostratus zone, and 

 the similar specimens from the Isle of Wight came from the sand- 

 stones underlying the Chert Beds on a corresponding horizon. 



Among other fossils found in the lower part of the clay at the 

 locality we are discussing are Nucida pectinata J. Sow., Pecten 

 (Syncyclonema) orbicularis J. Sow., and " Scalaria " dupiniana 

 d'Orb. ; but these are valueless in settling the question of age, 

 since their range extends up from the Gault into and above the zone 

 of Pecten asper. At about 8 to 10 feet above the base of the clay 

 further ammonites were found. These include a Hoplites of the 

 tuherculatus group, and another well-tuberculated species showing 

 smooth late growth-stages ; also a large involute hoplitid of flattened 

 discoid form, devoid of ornamentation and with narrow concave 

 peripheral area. This appears to represent an advanced evolutionary 

 stage in one of the several series whose members are commonly 

 united under the favourite collective name H. splendens. At this 

 level and in the overlying part of the clay there occur large crushed 

 examples of Inoceramus sulcatus, Park., a fact of much significance. 



At about 15 to 17 feet above the base these Inocerarni are associated 

 with numerous ammonites, including an undescribed Schloenbachia^ 

 characteristic of the rostratus beds, Schloenhacliia varicosa (J. de C. 

 Sow.) [= Hysteroceras of Hyatt], and several species of Mortoniceras 

 (the keeled ammonites of the rostratus group, sensu lalo), including 

 at least one belonging to the narrower group of M. infiatum 

 (J. Sow.). This association of forms, particularly the abundance 

 of Inoceramus sulcatus and Schloenbachia varicosa, points to a 

 position in the rostratus zone corresponding with Price's Bed IX at 

 Folkestone.^ This upper part of the clay is rather more limy, and 

 on drying becomes paler in colour than the lower part. The fact 

 that the Upper Gault along parts of the Bedfordshire outcrop shows 

 resemblance to the Chalk Marl has been frequently commented on. 



1 F. G. Hilton Price, A Monograph of the Gault, London, 1880, p. 20. " On 

 the Gault of Folkestone " : Quart. Journ. Geol. Soc, vol. sxx, 1874, p. 351. 



