part 4] jiTEASSic cheoxologt : lias. 293 



Genus Gtuibaliceeas, nov. (Figs. 14 & 18, p. 295.) 



Type, Am. guilalianus D'Orbigny.^ 



Distinct from Gleviceras by the intermittent character of its 

 ribbing and also by its sntm-e-line. Am. aballoensis Dumortier 

 j9«rs,2and AmaWieus guihalianus Wright pars^ {non D'Orbigny), 

 have the intermittent style of ribbing, and presmnabl}^ belong to 

 this genus. 



Genus YiCTOEiCEEAS, nov. (Figs. 13 & 19, p. 295.) 

 Type, Ammonites victoris Dumortier.* 



Distinct from Gleviceras by different suture-line, peculiar 

 character of test — striate and punctate,^ — dichotomous stjde of 

 ribbing and other characters. The dichotomy begins at the um- 

 bilicus, where there is a sort of bunching on the umbilical wall, and 

 is repeated at several stages across the whorl, with short costulse, 

 dichotomous or intercalated, on the periphery. 



Fine examples of Ammonites victoris occur With. RadstocJciceras 

 at Radstock, with many other remarkable Oxynotoids which must 

 be left for another opportunit3^ 



The suture-lines of some of these Oxynotoid genera are presented 

 in figs. 1-6, p. 294 :— 



Fig. 1. Oxyyioticeras oxynotum (Quenstedt), after his figure, Ceph, v, 11. 

 Figs. 2a & 2 6. 0. oxynotum (Quenstedt), from a paratype of Am. cultelhis 



J. Buckman in my collection, to show increase of complexity due to 



age. The specimen, wholly septate, measures 123 mm. (nearly 



5 inches) in diameter ; and suture-line 2 a is taken at a diameter of 



about 31 mm., 2 6 at about 90 mm. 

 Fig. 3. Oxynoticeras polyophylluin (Simpson), after the figure in ' Yorkshire 



Type Ammonites ' 1909, No. 8. 

 Fig. 4. Gleviceras glevense, genotj-pe, from the specimen figured in PI. XXVIII, 



fig. 2. 

 Fig. 5. Gleviceras glevense, holotype, from the large specimen illustrated in 



PL XXVIII, fig. 1. 

 Fig. 6. RadstocTciceras complicatum, from the specimen depicted in PL XXVII, 



fig. 1, the suture-line X 0"67 : from a photograph. 



To facilitate comparison of the various Oxynotoid genera, out- 

 lines of the external lobe and saddle and the superior lateral lobe 

 are given in figs. 8-14, p. 295 : — 



Fig. 8. Oxynoticeras oxynotvm, after Quenstedt, X 2-5. 



Fig. 9. 0. oxynotum {Am^monites cultelhis), see above, fig. 2 h. 



Fig. 10. 0. polyophyllum, see above, fig. 3. 



Fig. 11. Glevicei-as glevense, see above, fig. 4. 



Fig. 12. RadstocTciceras complicatum, see above, fig. 5. 



Fig. 13. Victoriceras victoris (Dumortier), after his fig. op. cit. pi. xxxi, fig. 1. 



Fig. 14. Guihaliceras gioihaliayium (D'Orbigny), after his fig. loc. cit. 



^ ' Pal. franc,-. : Terr. Jur. Ct^ph.' pi. Ixxiii. 



^ ' Bassin Rhone ' ii, pi. xxvii only. 



•^ ' Monogr. Lias Ammonites' 1881, pi. xlv, figs. 3,. 4 only. 



•* Op. cit. ii, pi. xlv, figs. 1 & 2. 



' See Dumortier, pi. xxxi, figs. 1 et 2. 



