H. B. Kirk. — On 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 (pis. iv. and v.) 



The systemic heart (pi. iv. i) 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 branchiae are the large branchial hearts (pi. v., fig. 1/), 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 (pi. v., fig. 1/'), 

 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 (pi. 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 (pi. v., 1 c) 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., h), 

 which, shortly after its commencement, divides into three branches, these 

 being borne along reflexions of the peritoneal membrane to the mantle. 



The branchial (pi. iv., g, g; pi. v., fig. 1) are large and prominent, the 

 tip extending to beyond the base of the funnel. About 70 non-ciliated 

 lamellae are given off on each side. The continuation of the branch of the 

 vena cava, 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 



