W. H. Hudleston—The Yorkshire Oolite. 291 
The upper portion of the body-whorl slopes outwards towards the 
principal varix or keel, except in the region immediately adjoining 
the suture. It is deeply ribbed and furrowed longitudinally. These 
ribs terminate in a similar set of tubercles, on the very prominent 
keel situated a little above the middle of the shell. The area between 
this and the second keel of the body-whorl is 20 mm. in length, 
and the ornaments are indistinct. This lower keel is less nodular, 
but has a marked effect on the general symmetry of the shell. The 
body-whorl is thus divided into three distinct areas, and the lowest 
third is distinguished by a wavy ribbing, which in some cases 
appears to bifurcate from the faintly-developed nodes.. The position 
of the shallow notch at the base of the shell is fairly distinct in this 
specimen, the front of which is too much buried in matrix to show 
the mouth properly. The mineral condition, too, is unfavourable 
for showing the finer ornaments, if such existed, and this should be 
borne in mind when making comparisons with the other figures : 
on the other hand, it is the only specimen I have ever seen with the 
margins unimpaired. 
Fig. 2.—Another specimen from the Coral Rag of Langton Wold 
(Yorksh. Phil. Soc.). 
IEP MENPOPEG). N. cle ai.g crete tah s.dletey afoot dce's 5 78 millimétres. 
Greatest width (restored)...........0 cece cece Bey) be 
Length of body-whorl to entire shell ........ 70: 100. 
PERN ATINE Psy Wid pafs aie pi +924 ep mils sts (ose aks ated 80°. 
This specimen is not quite so bold as the last, and is also much 
more imperfect in outline, but has enough of the shell properly 
preserved to show the well-marked transverse lines which decussate 
with the more or less wavy ribbing. The effect thus produced, 
which is almost like basket work, seems characteristic of all the 
varieties of this species. The mouth is wide, with a flattish base, 
which causes it to differ from Natica ; but the portion which should 
show the notch is broken away, as is unfortunately too frequently 
the case. The aperture is semi-ovate, wide, and slightly expanded. 
The inner lip is but slightly curved: it was thick, and originally 
extended further over the columellar region, but has been partly 
destroyed in cutting out the shell; this has produced an appearance 
like an umbilical groove, which, if it existed, must have been very 
slight. 
From the combination of these two specimens the average 
character of the species may be deduced. 
Fig. 4.—Specimen from the Coral Rag of North Grimston (my 
Collection). This variety, from the imperfect development of the 
second keel in the body-whorl, has somewhat closer affinities with 
P. Lapierrea, Buy. Yet, if Buvignier’s species be correctly figured, 
the mouth of the North Grimston specimen is very different. Ours 
is a handsome and striking form, and, should a sufficient number be 
found, might be raised to the dignity of a named variety. The 
spiral angle is 79°, being practically of the same value as in the two 
specimens previously described—an important point of resemblance. 
There is also the same kind of wavy ribbing, but it is more coarsely 
