PLATE 38, 39, 40, 41. 
Now and then found in our limestone, but not frequent. 
Fig. I. A specimen in brownish spar. The margin of 
the mouth broken : the striae on the back indistinct. 
2. Shows the back of another specimen in white spar: 
the striae acute and perfect. 
p. 40 — FIG. 3, 4. 
CONCHYLIOLITHUS Helicites? ( aiiricularis ) nva- 
bilicatus auriformis subdepressus, subtus concavus, 
ambitu subacuto, apertura ovali, anfractibus duobus : 
superiore minutulo laterali. S. p. 
A petrified shell. The original an Helix*? umbilicate,, 
ear-shaped, depressed, somewhat convex above ; beneath 
concave. Ambit somewhat acute. Aperture large, oval. 
T 
« We have ranked this fossil, for the present, as an Helicite, but not 
without some doubt of the family to which the prototype may properly 
belong. The genus Helix, as established by Linne, is confessedly an incon- 
gruous one : many of its species agree neither in that particulai part, from 
which the leading generic character is taken ( apertura coarctata, intus 
lunata f. subrotunda: — Syst. Nat.) nor in their general habit; and arc 
only connected by the merely artificial distinction of a more fragile and mem- 
branous structure than that of the other testacea : a characteristic wholly 
useless in discriminating the fossil subjects — and hence the diflEculty of detei- 
