73 



AMMONITES laviuscnlus. 



TAB. CCCCIA.—Jigs, I and 2. 



Spec. Char. Discoid, carinated, umbilicated, 

 obscurely radiated ; carina distinct ; radii 

 waved, alternately long and short, slightly 

 elevated ; umbilicus small, exposing parts of 

 the inner whorls ; aperture sagittate. 



One half of the diameter of the shell is occupied by the 

 aperture, a third of the other half by the umbilicus, in 

 full grown individuals ; in young ones the umbihcus is 

 larger. The front is obtuse with a large prominent keel 

 in the middle of it ; the sides are rather convex marked 

 with waved, elevated radii, that are broader and less 

 conspicuous on the outer whorls of the full grown shells. 

 In young shells the aperture is oblong, rather square ; as 

 the shell grows older, the aperture becomes longer, more 

 deeply notched by the preceding whorl, and narrower 

 towards the front. 



Found in the inferior or Ironshot Oolite, at Dundr y 

 by G. W. Braikenridge, Esq. to whose liberality we are 

 indebted for a scries of specimens. 



