NUMMULARIA. CEPHALOPODA. 19 
intersecting the curved edges of the transverse partitions at a number of points, 
naturally divide them into a series of curvilinear parallelograms; the two 
shorter sides of each parallelogram being formed by the edges of transverse 
septa, whilst its two longer sides are formed by segments of the external ribs 
and strie, or the lines of growth. 
In these Fossil Nautili which had not been fractured in the catastrophe 
by which they were overwhelmed, and the hydraulic actions of the siphuncle 
not having been affected, the air chambers are generally filled with calcareous 
spars, which appear to have been subsequently introduced by infiltration of 
water, holding in solution carbonate of lime, after the animal matter of the 
shell had been decomposed. In other cases, where the siphuncle had been 
broken, or the external shell fractured, the chambers are filled by the mud or 
limestone in which they were imbedded. ks 
Two new genera have been proposed, as connected with Nautilus, viz. 
Genus XIII. — ENDOSIPHONITES, — A discoidal, 
nautiliform shell, with the siphon situate close to the body 
volution, which constitutes its chief distinction from Am- 
monites. 
Endosiphonites carinatus. Plate VI. fig. 3. Found in 
the Cambrian strata, Cornwall. 
Genus XIV.—SIMPLEGUS. — Blainville. — Discoi- 
dal and multilocular, with the spire uncovered like the 
Ammonites; but having the chambers divided by simple 
septa, as in Nautilus. 
Simplegus sulcata. Plate VI. fig. 4. 
Genus XV.— NUMMULARIA. — Lamarck. 
Generic Character. — Shell lenticular, disciform, or thick 
in the middle, and attenuated towards the margin; spire 
internal, multilocular, covered over by several tables ; volu- 
tions generally numerous, sometimes to the number of 
twenty; the outer wall of the volutions complicated, ex- 
tending and uniting on each side at the centre of the shell ; 
cells very numerous, sinall, alternate, and formed by trans- 
verse imperforate septa, which are convex near their fronts, 
leaving a fissure between each of them and the preceding 
volutions; their sides are narrow, variously curved, and 
extending to the axis. 
N. rotulata. Plate II. fig. 18. This species is found at 
Meudon, France, and is a member of the genus Lenticulina, 
now united to this genus. 
Nummularia levegata. Plate II. fig. 6 and 7. 
There are but few species of this genus, and these are chiefly found in the 
Calcaire Grossier. They have a very wide geographical range, having been 
‘met with in France, Germany, Switzerland, Spain, Egypt, and England. 
