cut short).

m, The hood or dorsal enlargement of the annular lobe of the
fore-foot.

n, Tentacles of the annular lobe.

p, Tentacles of inner inferior lobe.

q, Buccal membrane.

r, Upper jaw or beak.

s, Lower jaw or beak.

t, Lingual ribbon.

x, The viscero-pericardial sac.

n.c, Nerve-collar.

oe, Oesophagus.

cr, Crop.

gizz, Gizzard.

int, Intestine.

an, Anus.

nept, Aperture of a nephridial sac.

r.e, Renal glandular masses on the walls of the afferent branchial
veins (see fig. 11).

a.b.v, Afferent branchial vessel.

e.b.v, Efferent branchial vessel.

vt, Ventricle of the heart.]

Posterior salivary glands are not developed in _Nautilus_, but on each
side in the wall of the buccal mass is a gland corresponding to the
anterior salivary gland of the Dibranchiata. No ink-sac is present in
_Nautilus_.

[Illustration: FIG. 11.--Diagram to show the relations of the four
nephridial sacs, the viscero-pericardial sac, and the heart and large
vessels in _Nautilus_ (drawn by A.G. Bourne).

neph, neph, on the right side point to the two nephridia of that
side (the two of the opposite side are not lettered)--each is seen
to have an independent aperture.

x is the viscero-pericardial sac, the dotted line indicating its
backward extension.

visc. per. apert, marks an arrow introduced into the right aperture
of the viscero-pericardial sac.

r.e, r.e, point to the glandular enlarged walls of the afferent
branchial vessels--two small glandular bodies of the kind are seen
to project into each nephridial sac, whilst a larger body of the
same kind depends from each of the four branchial afferent vessels
into the viscero-pericardial sac.

v.c, Vena-cava.

vent, Ventricle of the heart.

ao, Cephalic aorta (the small abdominal aorta not drawn).

a.b.v, Branchial vessel.

e.v.b, Efferent branchial vessel.]

_Coelom, Blood-vascular System and Excretory Organs._--_Nautilus_ and
the other Cephalopoda conform to the general Molluscan characters in
regard to these organs. Whilst the general visceral cavity forms a
lacunar blood-system or series of narrow spaces, connected with the
trunks of a well-developed vascular system, that part of the original
coelom surrounding the heart and known as the Molluscan pericardium is