166 



PALAEONTOLOGY 



LATERAL 

 AREA 



* 



L) f 



INNER OR 



UMBILICAL/' p RE 5 o> 

 AREA /&*jmjfr\ 



FIG. 49. WHORL-SHAPE IN AMMONOIDEA. 



All except e, g, and A are apertural views, a. Microderoceras, lat-umbili- 

 cate, rotiform, whorl-section quadrate, b, Dactylioceras. lat-umbili- 

 cate, planulate, whorl-section rounded, c, Chamousettia, angust- 



