XAUTILID^, 
113 
The whorls are all exposed, with a small central perforation : 
they are roughly hexagonal in section, the periphery in the young 
and adolescent stages of growth being bordered by an acute keel, 
which disappears in the adnlt. Two very obtuse keels or pro- 
minences are developed on the periphery, but these are scarcely 
perceptible in full-grown individuals, save that in some specimens 
their presence is indicated by a more or less distinct furrow along 
the median line The body-chamber occupies about half a volution, 
its apertui'e forming a sigmoid curve at the sides and a deep sinus 
upon the periphery. The surface of the test when weU preserved is 
seen to be marked with fine striae, of which four or five occupy the 
space of a line. The surface of the internal cast of the body- 
chamber is marked by a series of punctures arranged in lines which 
conform to the outline of the aperture, at the margin of which there 
are a number of crennlations which may indicate corresponding folds 
on the borders of the mantle, the punctures doubtless representing 
its surface. 
A little above the base of the body-chamber the impression of the 
retractor muscle is seen upon the casts of well-preserved specimens. 
This is particularly well shown in a specimen from Ireland, registered 
No. 50190 (fig. 15, D), and also in No. 43861 (fig. 15, C), the latter 
forming part of the “ Sowerby Collection.” 
Sowerby observes that “ the lesser keels in lY. cariniferus disappear 
as it advances in growth ; it may possibly therefore be only a variety 
of N. hiangulatus : the specimens with keels are, however, much 
larger than the specimen figured.” 
Not having seen the type specimen of N. hiangulatus, \ am unable 
to say anything definite about its affinities with the present species, 
but judging by Sowerby’s figure I should suppose that it might be 
only an immature example of it. 
Figure 4 (of Sowerby’s plate cccclxxxii.) I take to be a fragment of 
C. paucicarinatus ; but the specimen not being now in the “ Sowerby 
Collection,” I have no means of verifying this impression. 
Horizon. Carboniferous Limestone. 
Localities. Cork, Kildare, Kathkeale (Co. Limerick) ; Lolland, 
Yorkshire : Thornley Quarry, Chipping, near Preston (Lancashire). 
llepresented in the Collection by a large number of specimens, 
including one of Sowerby’s types (“ Sowerby Collection ”) figured in 
the ‘ Mineral Conchology,’ tab. cccclxxxii. f. 3. 
1 A. mlciferus, Phillips {loc. cit.). 
PART II. 
I 
