78 
expansion from the next turn, the rugas of which are continued very 
closely and regularly up this central projection, to where it has been 
broken off : this is formed by two flattish turns, which, on their upper 
surface, are marked by slight longitudinal rug®, which terminate in 
two ridges, disposed on the inner and on the outside of each turn. 
These turns, on the lower side, are roundish, and are very thickly set 
with sharp and irregular rugae, and seem to form a concavity nearly 
corresponding to the elevation on the other side ; but in this concavity 
an irregular shelly body exists, which appears not to be accidental, 
but a part of the original shell. Fig. 7 represents the under part, 
with this irregularly formed body, and Fig. 8 represents the upper 
surface, with its projecting central termination. An endeavour is 
made to give a representation of the aperture of this shell, of which 
description could hardly have given a satisfactory idea ; indeed, it is 
so much obscured by the surrounding matrix, as to prevent a correct 
figure of it being obtained. The matrix of this fossil is a yellowish 
lime-stone, with which the hollow of the shell is completely filled. 
The fossil, PI. V. Fig. 18, which appears to be of the same genus with 
the two preceding, is so figured, as to show a portion both of its upper 
and under part. On the former, the turns of the spire are seen covered 
with closely-set transverse ribs, the spire terminating in a roundish 
projection. The turns of the spire are ribbed in the same way on the 
under side; and here a projecting shelly body is seen in the concave part, 
answering, in its situation, to the irregular formed body in the preceding 
fossil ; and to the projecting superior termination of the spire in the 
same fossil, in having the markings of the spiral turns continued upon it. 
It would be premature to attempt to establish a genus for the 
reception of these fossils, until more particulars are ascertained 
respecting the original size and real nature of the projecting bodies 
which appear to belong to both the upper and under surface of these 
fossils. Should the appearance of these be found to be constant, that 
alone would, of course, form a generic distinction. 
