154 Records of the Indian Museum. [VoL. XT, 
The vessels are connected to the dorsal sinus in the mid-dorsal 
line of the body wall. In other respects, the body wall is quite 
similar to that in other species. 
II. Pallial Complex. 
The pallial complex forms a circular area extending from the 
right side at the junction of the inner surface of the mantle and 
the dorsal surface of the foot to within 6 cm. of the margin 
of the mantle on the lett side. It lies at about 2.4 cm. distant 
from the anterior margin of the mantle. The pericardium lies 
in the anterior two-thirds of the pallial complex and to the right, 
the kidney occupying the remainder. There is no distinct pul- 
monary chamber at all. The whole pallial complex is adherent to 
the thick mantle and is rocfed by a thin membrane which is fused 
with the inner surface of the latter. The ventral wall lies over 
the anterior end of the liver. 
The heart is placed in the long axis of the pericardium. The 
auricle is placed behind the ventricle. 
Minute structure of the ventricle.—The outer surface is lined by 
a single layer of cubical-cells with oval nuclei. There is no 
distinct epithelial lining of the cavity. The superficial layers form 
a thin continuous coat of transversely-arranged muscle fibres. 
Beneath this, the muscle fibres form thick bundles which are 
disposed irregularly in different directions. Just beneath the 
superficial layer, the thick bundles are arranged circularly in a 
transverse direction, being separated from the former widely in 
many places by thick bundles which pass inwards, some radially 
and others obliquely, from the superficial bundles to these circu- 
lar ones with which they seem to unite. More internally the 
disposition of the fibres are mainly longitudinal with a few oblique 
ones. The cavity of the ventricle is traversed by these muscle 
bands which extend through the cavity in various directions. 
Minute structure of the auricle.—The wall is lined externally 
by a layer of rectangular cells with their long axis parallel to 
the surface. ‘The superficial muscles form a transversely circu- 
lar layer. ‘The inner bundles form a longitudinally circular layer. 
Between these two layers, there are a few bundles which are 
arranged obliquely and seem to pass from one layer to another. 
III. Digestive System. 
(i) The buccal bulb forms a protrudable proboscis which, 
when retracted, is placed inside a proboscis sheath having a 
narrow tunnel-like shape at its outer aspect. The proboscis forms 
the acrecbolic (pleurembolic) introvert of Sir KE. R. Lankester. 
As seen in a longitudinal section, the proboscis, when re- 
tracted, lies in the tubular space formed inside the proboscis 
sheath, which is folded a little behind its middle in such a way 
that its posterior portion is invaginated into the anterior portion ; 
