H. B. Kmx.—0On the Anatomy of Sepioteuthis bilineata. 151 
at about three-fifths of the total distance from the apex, where the breadth 
is about one-tenth of the length. The gladius is lodged in the anterior 
aspect of the mantle; and the posterior wall of its chamber is formed by a 
tough transparent coat, whose consistency approaches that of cartilage 
where it covers the apex. The gladius extends the whole length of the 
mantle. 
Circulatory and Respiratory Organs (pls. iv. and v.) 
The systemic heart (pl. iv. d) lies about the centre of the pervisceral 
cavity. In shape it is nearly triangular, the base of the triangle lying 
towards the oral end of the body. ‘The right side is the larger, owing to 
the great cephalic aorta being given off from this side. Lying at the base 
of the branchise are the large branchial hearts (pl. v., fig. 17), globosely 
ovoid in shape, and with their axis forming an acute angle with that of the 
body. At its inner end each has a small fleshy appendage (pl. v., fig. 17”), 
and each is encased in a chamber with transparent membranous walls 
(id., k). 
As it approaches the heart the vena cava (id., b) divides, one branch 
going on each side of the intestine at its point of flexure and entering the 
branchial heart on its upper surface. Veins (pl. iv., v, v) are seen converg- - 
ing on the inner side of the mantle to enter the vena cava. These cross 
from the mantle by the peritoneal membrane which is thickened for the 
purpose. Similar veins run from the anterior aspect of the body, entering 
the vena cava with those from the sides of the mantle. 
After passing from the branchial heart through the gills the blood enters 
the systemic heart at the two dilatations (‘‘ auricles”) already noted as 
giving the triangular shape to the heart. The left auricle is the more 
strongly marked, the right being somewhat obscured by the great develop- 
ment at the point whence the cephalic aorta (pl. v., 1c) is given off. 
Shortly from its commencement this aorta gives off branches to the liver. 
At its opposite end the heart contracts to give off the posterior aorta (id., A), 
which, shortly after its commencement, divides into three branches, these 
being borne along reflexions of the peritoneal membrane to the mantle. 
The branchie (pl. iv., g, g; pl. v., fig. 1) are large and prominent, the 
tip extending to beyond the base of the funnel. About 70 non-ciliated 
lamelle are given off on each side. The continuation of the branch of the 
vena caya, after passing through the branchial heart, forms the central axis 
of the gill on the anterior side; and it is attached throughout the whole 
length of the gill by a suspensory membrane (id., a) to the anterior mantle 
surface. On the posterior side, the branchial vein forms the central axis. 
Each lamella is bordered by two capillaries, one running from each of the 
axes of the gill and meeting at the apex of the lamella, and themselves 
