1911 



YORKSHIRE TYPE AMMONITES 



XXIXa 



Fig. I 



Fig. 2 



Ammonites vortex, Simpson, 1855 



Whitby Mu.seum, No. 153a, Holotype 



Fig. I, Side view ; Fig. 2, Apertural view 



PORPOCERAS VORTEX, Simpson sp. 



