MOLLUSCA. CEPHALOPODA 



277 



Macrocephalites. Shell without a keel, whorls largely em- 

 bracing, external margin rounded, umbilicus small. Ribs numerous, 

 dividing near the umbilicus, continued over the external margin, and 

 without tubercles. Aperture without lobes. Sutures deeply divided, 

 with auxiliary lobes. Great Oolite to Kellaways Rock. Ex. M. 

 macrocephalus, Cornbrash. 



Fig. 118. Stepheoceras (Normannites) braikenridgei, from the Inferior 



Oolite, x #. 



Cardioceras(fig.ll9). Shell 

 flattened ; whorls considerably 

 embracing, with strong curved 

 ribs which bifurcate, and bend- 

 ing forward near the external 

 edge join the notched keel ; short 

 ribs often intercalated on the ex- 

 ternal part. Lobes and saddles 

 moderately divided ; two short 

 lateral lobes, and two or three 

 auxiliary lobes ; internal lobe with 

 a single point. Kellaways Rock 

 and Oxfordian. Ex. G. cordatitm, 

 Oxfordian. 



Fig. 119. Cardioceras cordatum, 



from the Oxfordian. 





Perisphinctes. Shell discoidal, external margin rounded ; 

 umbilicus generally large. Ribs straight, continuous, bifurcating 



