part 4] EVOLUTION of the liparockkatid.i:. 277 



C. Androgynoceras: 



Androgynoceras maculatttm (Young- & Bird). 



Refigured by S. S. Buckman (1, vol. i, No. 45). 



Non A. maculatum Wright (8, pi. xxxiv). 

 Non A. maculatum Quenstedt (4, pi. xxxiv). 



Androgynoceras obtusicosta, sp. nov. (PL XXII, figs. 2 a 



&2b.) 



Compare A. maculatum (=capricornum) Wright (8, pi. xxxiv, figs. 4 & 5). 

 A. maculatum Quenstedt (4, pi. xxxiv, fig. 5). 



Dimensions of holotype : — 



Diameter. Whorl height. Whorl thickness. Umbilicus. 



80 mm. 34 per cent. 26 per cent. 46 per cent. 



An evolute Capricorn, bituberculation commencing. Whorl round 

 up to a diameter of 50 mm., after which it becomes more elevated. 

 Kibs pass directly across the venter and are very little diminished ; 



Fig. 7. — Suture of Androgynoceras obtusicosta {Lincoln). 



50 mm. 



round, 23 on the outer whorl, separated by wide spaces. Fine 

 stria? between the ribs, especially on the periphery. 



The suture shows a deep external lobe divided by a high median 

 saddle ; wide external saddles, first lateral lobes narrow and asym- 

 metrically divided (text-fig. 7). 



Occurrence. — Latcecosta sub-zone, Lincoln. 



Distinguished from JEcjoceras latcecosta by the suture and by the 

 prominence of ribs on the periphery. With A. obtusicosta occur 

 other ammonites in which the outer whorl is swollen, the Capricorn 

 staa'e commencing later and bituberculation earlier. These forms 

 constitute a transition to A. hi/brida (A. d'Orbigny). 



Androgynoceras hybreda (A. d'Orbigny). 



Ammonites liybrida d'Orbigny (3, pi. lxxxv, figs. 1-3, non figs. 4-5) ; com- 

 pare A. intracavricornus Quenstedt (4, pi. xxix, fig. 0). 



This is the Jijsterogenes-stsige of this scries ; its connexion with 

 these ammonites is supported by the asymmetrical first lateral lobe 

 and the proportions of the suture. The young figured by A. d'Or- 

 bigny probably is from a different ammonite, resembling Oistoceras* 



