BLOOD-VASCULAR SYSTEM, ETC., OF AMIURUS CATUS. 4933 
posterior end. This vessel passes directly downward through the 
substance of the kidney to the mesentery, and anastomosing with 
the left mesenteric artery is distributed with it to the rectum. 
The descending aorta behind the origin of the cceliaco-mesenteric 
artery enters a deep groove (Pl. IV., Fig. 7) on the ventral surface 
of the fourth vertebra to pass the attachment of the air-bladder. 
Throughout the rest of its course in the body-cavity it lies upon the 
rounded surfaces of the centra. In the tail as the art. caudalis it 
occupies the bottom of a groove on the centra, and is further pro- 
tected by the hzmal arches and by the short spines which arise from 
the sides of the groove between these arches. A longitudinal dorsal 
ridge projects into its lumen as in some other forms. 
The arteries given off to the trunk and tail arrange themselves in 
three sets, newral, lateral and hemal. Each pair of neural and 
lateral branches arise by common stems, which, passing around the 
vertebra, give off the lateral arteries about the middle of the centrum, 
and are then continued upwards along the posterior surface of the 
neural spine as the neural arteries. 
The /ateral arteries pass outwards by the division in the lateral 
trunk musculature along the ‘lateral line,’ giving branches to these 
muscles. , 
The newral arteries divide into branches which run between the 
lateral muscles and supracarinales, and branches which pass upwards 
in the median line between the supracarinales. 
The hemal arteries have similar relations to the ventral muscles. 
They arise independently, and run upon the anterior surface of the 
hemal spine. Throughout the length of the body cavity these 
arteries (tntercostales) run with the nerves between the peritoneal 
lining and the muscles of the body wall. 
These vessels present the same irregularity in Amiwrus as is found 
in other Teleoster. A large number have entirely disappeared or 
been greatly reduced in size, and the blood is distributed by large 
single stems, now from the right side and now from the left, giving 
branches to both sides of the body and spreading over from two to 
five myomeres. 
The lateral arteries and the hemal arteries of the body cavity can, 
from their position, supply only one-half of the body, and conse- 
qnently present greater regularity than the others. 
