HOTZ. | H. J. FLEURE: Anatomy of Melo indicus. 4II 
the auricle above (technically forwards and to the left) and by the 
base of the aorte below. The pericardial cavity is fairly spacious 
and its connection with the renal organ is on the posterior or right 
side of its floor. The pericardial lining does not seem to possess 
glandular specialisation though my specimens were not in a con- 
dition for histological examination. The ventricle is strongly 
muscular, with the muscle internally in longitudinal bands, the 
bands being radially arranged. The auricle was strongly con- 
tracted in the specimens examined, but a valve seems to exist 
between it and the ventricle. 
The base of the aortae is guarded by a pocket valve on the 
side towards the anterior aorta and the wall projects inwards 
from the side towards the posterior aorta; these arrangements 
must be effective against back-flow. 
There are as usual two aortae. 
The anterior aorta is strongly walled and follows the oeso- 
phagus for some time (pl. xxxi, fig. 9), giving off several branches 
to bodywall, columellar muscle and foot across it. A large branch 
goes to the siphonal region, and the anterior region generally. 
The visceral aorta is also strong and it divides as shown in 
fig. Q. 
The spaces throughout the body are blood spaces. They may 
be grouped, more or less, into sets :— 
(a) The spaces in the foot, often running along with the 
nerves. 
(b) The general anterior cavity continued into the cavity 
of the proboscis. This cavity communicates with 
the spaces in the foot more especially, though not 
exclusively, in the neighbourhood of the pedal 
ganglia. 
(c) The spaces between and amongst the parts of the renal 
organ, reproductive organs, and intestine, 7.¢., the 
lower part of the visceral mass. The connection of 
these spaces with those of the anterior cavity appears 
to be regularized into what is practically a vessel 
(pl. xxxii, fig. 16, Ant. V.) and certainly these spaces 
are, otherwise, practically completely cut off from 
those under (a) and (0). 
(d) The spaces amongst the parts of stomach and liver, 
?.e., in the upper part of the visceral mass, somewhat 
distinctly marked off from those under (c) with 
what may be called an anterior visceral sinus. 
{e) The spaces in mantle roof, cteniduim, and siphon. The 
afferent channel to the ctenidium continues the 
anterior visceral sinus. These spaces, especially 
towards the siphon, are also in connection with those 
of the general anterior cavity (b above). The 
afferent ctenidial channel is well marked. 
