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NUMMULARIA. 
Nummulites, Lamarck. 
Gen. Char. A lenticular,, involute, chambered, 
univalved shell, with similar sides ; whorls 
closely embracing each other and penetrated 
by small columns ; septa convex near their 
fronts, leaving a fissure between each of them 
and the front of the preceding whorl ; their 
sides narrow, variously curved, extending to 
the axis. 
Notwithstanding the introduction of several distinc- 
tions not noticed by Lamarck, and other modifications 
of the generic character for the purpose of accuracy and 
of distinguishingNummulitesfrom other exuviae of sup- 
posed Cephalopodous Mollusca, we have not been able 
to exclude Lamarck’s genus Lenticulites, the species of 
which only differ in general form or trivial characters 
from Nummulites : in fact, the two characters which 
Lamarck points out to distinguish the Lenticulites by, 
both exist in Nummulites, but have been overlooked : 
the small fissure between the edge of each septum and 
the margin of the preceding whorl has not before been 
noticed ; it occurs both in the Nummulites and Lenti- 
culites of Lamarck, and so do the small columns that 
penetrate from one side to the other parallel to the axis, 
and sometimes form protuberances upon the surface. 
The whorls appear to be completed at various periods 
of growth by three or four chambers gradually diminish- 
ing from the centre, until the last extends only to the 
