314 
however, they are united by a longitudinal trunk, the lateral hypo- 
branchial (A’brn. 1.)'), which, besides giving rise to anterior nutrient 
branches, turns at ab- 
out the region of the 
fourth arch and as a 
probable representative 
of the fourth commis- 
I sural artery (coms. JV) 
extends to the ventral — 
side of the ventral 
aorta (ao. v.). Here it 
unites with a corre- 
sponding artery from 
the opposite side of the 
body and thus gives rise 
to the median hypo- 
branchial (h’brn. m.). 
This vessel extends 
ar \ 
“a da 
The Heart.and Right Gills with their Principal Blood Vessels in Orthagoriscus 
mola seen from the Right’Side. The four gill arches are cut through and the parts of 
the first three gills attached to the afferent arteries are reflected dorsally. Abbreviations: 
ao. v. ventral aorta. aur. auricle. coms. IV. fourth commissural artery, coms. VI. sixth 
commissural artery. cor, d. dx. right dorsal coronary artery. cor. v. ventral coronary 
artery. e’ga. epigastric artery. A’drn. l. lateral hypobranchial artery. A’brn. m. median 
bypobranchial artery. wn. superficial vein opening into auricle, vn‘, superficial vein 
opening into venous sinus. vnt. ventricle. III. IV. V. VI. third, fourth, fifth, and sixth 
visceral arches. 
towards the heart, near which it divides into two branches, the 
epigastric artery (e’ga.), to the muscles about the pericardial space, 
and the ventral coronary artery (cor. v.), designated by MıLnk Epwarps 
(58, p. 341) as Vartére coronaire inférieure, to the vents side of the 
ventricle. 
The efferent artery of the right sixth arch (VI) gives rise to a 
single vessel, the sixth commissural artery (coms. VI), which makes 
its way ventrally to the right dorsal side of the ventricle, where, as 
the right dorsal coronary (cor. d. dx.), it is distributed to the muscular 
part of this organ. A corresponding vessel symmetrical with this takes 
its origin from the left sixth arch and is distributed to the left dorsal side 
of the ventricle. As is shown in the figure, these right and left sixth 
1) For the terminology used in this paper the reader is referred to 
Parker and Davis, ’99. 
