26 
NAUTILOIDEA. 
character, being sometimes rounded, sometimes more acute, but 
always rough [? eroded]. On the average they are about h the 
whorl-breadth apart, or 26 per whorl, growing closer with age. 
They are direct on the inside when exposed, and curve hack on the 
sides to meet at a rounded angle on the front, where they either 
become feebler with intermediate ribs, or break up into smaller 
ones ; the whole are generally continued to the aperture, but the 
ribs are sometimes replaced by lines of growth. The surface is 
seldom well enough preserved to show the parallel lines of growth 
on the ribs, but often the epidermids of the under layer are visible. 
These are direct, crossing the ribs, from 14 to 22 per line. There 
are also longitudinal ones on the inner side when exposed. The 
body-chamber always includes part of the normally-coiled portion, 
and extends a variable distance in a nearly straight line. The 
largest seen was 8 inches long, but it is impossible to say what 
proportion this bore to the coiled portion. This and several smaller 
ones show no difference on approaching the aperture, which seems 
to be indicated by the deep back-curving ribs ; but in one or two 
instances there is a decided contraction just at the aperture on each 
side of the whorl, as in fig. 2, dividing it, as seen in full view, into 
two wider portions, separated by a narrower, and yet not forming 
a contracted aperture in the same sense as in the Fhragmocerata. 
The septa are direct across the front ; but on the sides, their general 
direction being radial, they become concave at some part, so that 
they cut across the ribs, and do not coiucide with the epidermids, 
and they thus, on the whole, become sigmoid in form. They do 
not bear a fixed proportion to the ribs, but are sometimes more, 
sometimes fewer, the last few being closer, up to the whorl- 
breadth. The convexity of the septal surface is pretty constant at 
at about y the whorl-breadth. The siphuncle is nearly invariable, 
a little beyond [above] the centre.” (BlaJce.) 
Remarhs. This species bears a general resemblance to T. optatum^ 
Barrande (pi. xxiii.), but the septa are much closer, and the 
siphuncle, according to Prof. Blake, is nearer the centre. T'lie finer 
ornaments of the test, which are very characteristic in T. optatum, 
and consist of regular longitudinal striae crossing the ribs and the 
interspaces, have not been seen in the present species. It should 
be remarked that the figure of T. giganteum given by Professor 
Blake does not agree in some points with that of Sowerby, though 
both are alleged to have been drawn from the type specimen. 
Horizon. Lower Ludlow. ^ 
Locality. Leintwardine, Herefordshire. 
Bepresented in the Collection by two examples. 
