7920 AMMONITIDM 13 



Thus some tuberculation formulas are 

 O Procerites L 1 O 



O Trilobiticeras (L 2 ) 



O Otoites L 2 



and see Trueman : — 



O O Liparoceras (L 1 2) S^L 2 , that is, on L 2 partition. 



OO Becheiceras (L 1 3), (L 2 1). 



O O Androgynoceras OL 1 , O L 2 



O O Amblycoceras OL 1 , (S 1 ) 



When lobes develop laterally, expanding in some cases even to 

 invading their neighbours' territory, attention would not be paid to 

 these expansions for formula purposes — the main stems of the lobes 

 would give the position. 



Furcation : When the tubercle has not developed, or has declined, 

 so that the rib shows no swelling, the place where the tubercle will arise, 

 or where it may have been, is marked sometimes by rib-furcation. The 

 position of this may be important, and can be noted by the same 

 formulae, using, however, instead of O, the sign V. The signs OV 

 indicate that the tubercle is the furcation point, enclosed where necessary 

 within the brackets to show that the position is in the line of the area 

 of lobe or saddle. 



Family LI PA ROC ERA TIDM 



See II, v, B ; also Dr. A. E. Trueman, " The Evolution of the 

 Liparoceratidse " ; Abs. Proc. Geol. Soc. No. 1022, 1918, p. 65, Q.J.G.S., 

 LXXIV, 1919, p. 247. 



The following new genera are proposed — Trueman, 1918, p. 66 : — 



Parinodiceras, " Genoholotype, Am. striatum parinodus Quenstedt 

 ([Amm. Schwab Jura], 1884, pi. xxviii, fig. 6) " ; 



Becheiceras. " Genoholotype, Ammonites [Mgoceras] bechei Wright 

 (Lias Amm., pi. xli, fig. 1) " ; 



Anisoloboceras. " Genoholotype, Ammonites nautiliformis 



J. Buckman, [Y.T.A., I, 37, Pis. XXXVII a, b.] " and see II, xv. 



Trueman 1919, p. 264 : — 



Vicininodiceras. '' Genoholotype, V. simplicicosta, sp. nov. [p. 289]. 

 PI. xxiv, fig. 4." 



And in the same publication (p. 262) he discusses 



Amblycoceras Hyatt, 1900, "Genoholotype: A.capricornus Hyatt 

 in Eastman-Zittel, ' Text-book of Palaeontology,' 1st ed. vol. i (1900) 

 fig. 1204, p. 578." 



Family AMMONITIDM (ARIETIDM) 

 See Y.T.A., II, b and Oxynoticeras, Y.T.A., I, ii. 

 Oxy gastric, Ambly gastric : Pompeckj used these terms to denote 

 differences in the degree of sharpness acquired by narrow peripheries 

 of ' Oxynotes ' (Oxynotic. ; ' Comm.' Serv. Geol. Port. VI, 1906, 7, p. 291) ; 

 more or less of a knife-edge — oxygastric ; a blunt edge or narrowly 

 rounded venter — amblygastric. For use with oxycones and platycones. 

 Their employment with oxycone is no more tautological in the one case 



