280 ME. s. s. BUCKMAi^ ON [vol. Ixxiii, 



(2) Remarks on the Zones. 



The turne7n=semicostatum Zone (pars) auctt. — More than one 

 species of Arietites passes under this trivial name ; it is, therefore, 

 desirable to indicate the form intended. This is an evolute shell, 

 with compressed sides, and rectangular whorl-section, agreeing 

 with the upper figure in pi. cccclii of the ' Mineral Conchology,' 

 but not with Wright's figs. 1-3 in pi. xii of his 'Monograph of 

 the British Lias Ammonites.' 



Numerous specimens of Arnioceras are associated with A, tur- 

 neri in this district, but since Arnioceras spp. also occur abun- 

 dantly in the sauzeanum-gmuendense zones, while A. turneri 

 is not found at these levels, the last-mentioned makes the better 

 zonal fossil. 



The sauzeanum to conyheari Zones. — These zones are well 

 exhibited in the quarries about Keynsham. The beds are of no 

 great thickness, but they are very fossiliferous, and the faunal 

 succession is quite clear. North and south of Keynsham some of 

 these zones are missing, notably conyheari and rotiforme, while 

 paucity of deposit and penecontemporaneous erosion have resulted 

 in considerable compression of those remaining. 



The aiigulata, liasicus, and megastoma Zones. — The beds con- 

 taining numerous species of Sclilotheimia are well developed over 

 much of this district, although rarely complete at any one place. 

 Careful study of these beds has suggested division into two, well- 

 marked zones which have more than local application. The 

 angulata zone is thus restricted to the beds in the upper part of 

 the series. These beds contain, in addition to the index-ammonite 

 and numerous allied species, an abundance of SliyncJionella calci- 

 costa Davidson (non Quenstedt). In the lower division {liasicus 

 zone) Alsatites liasiciis (D'Orbigny), Sclilotlieimia gallica S. 

 Buekman, and Ornitliella sarthacensis (D'Orbign}^) are common 

 fossils, and they do not pass into the upper division. 



No species of Wcehneroceras have been obtained in this district, 

 and a non-sequence between jolinstoni and liasicus deposits is 

 therefore assumed. Ammonites of this genus have, however, been 

 recorded from Hock Cliif, near Fretherne (Grloucestershire),! and 

 from Evesham (Worcestershire). ^ 



An important JVcBhneroceras fauna occurs at Kayes Cement- 

 works, Long Itchington, near Southam (Warwickshire). The 

 extensive quarry at this place shows the following sequence : — 



conyheari. Vermiceras spp., Coroniceras spp. 



J , J Schlothehnia angulata, Schl. striata (Quenstedt). 

 ^ ■ |_ Rhynchonella calcicosta Davidson. 



/ Alsatitea liasicus (D'Orbigny), Schlotheimia spp. 

 Ornithella sarthacensis (D'Orbigny). 



megastoma. 



{ 



J Wsehneroceras extracostatum (Waehner), 

 \ with many other examples of the genus. 



1 L. Richardson, Proc. Cotteswold Nat. F. C. vol. xvi (1908) p. 141. 



2 S. S. Buckman, ibid. vol. xv (1906) p. 246 & pi. x, figs. 5-6. 



