BLOOD-VASCULAR SYSTEM OF THE LORICATI 55 
or efferent pseudobranchial artery (Pls. I, II and II, figs. 1, 5, 
I5, I9 and 20; Oph.A.), which supplies only the choroid coat 
of the eye.” This vessel pursues a dorso-cephalic course, pas- 
sing along the outer posterior edge of the levator arcus palatini 
muscle to the parasphenoid bone; it then runs parallel to the 
parasphenoid for a short distance, and when the anterior surface 
of the dorsal parasphenoid process is reached, sends off a 
branch inward in front of this process to anastomose with the 
corresponding artery from the opposite side. Here the main 
stem bends dorsad nearly encircling the orbito-nasal artery, and 
passing between the inferior and internal rectus muscles in 
company with the ramus ciliaris brevis and the ophthalmic vein 
it follows along the posterior surface of the optic nerve, but be- 
fore penetrating the sclerotic coat the artery makes a dorsal 
curve around the ciliaris brevis and the ophthalmic vein, and 
pierces the eyeball a little dorso-caudad of the optic nerve. 
After passing through the silver layer of the choroid it bifur- 
cates in the vascular layer of the choroid into an anterzor 
choroid artery (Pl. Il, figs. 20 and 21; Chor.A.,) and a 
shorter Posterior choroid artery (Pl. ILI, figs. 20 and 21: Chor. 
A.@). These 2 vessels have somewhat the shape of a horse- 
shoe, having its curved end dorsad and its open end ventrad. 
Radiating from the outer surface of this horseshoe-shaped vessel 
are numerous short vessels, which soon break up into smaller 
vessels, and these in turn break up into minute parallel capil- 
laries, forming the arterial retia mirabilia (Pl. III, figs. 19, 
20 and 21; A.Ret.M.) of the so-called choroid gland or vaso- 
ganglion, which has already been accurately described by Jones 
(41), Miiller (50), Stannius (74) and Emery (24). Distally these 
capillaries reunite, forming the chorozd arterzes proper (PI. III, 
figs. 20 and 21; Chor.A.), which supply the choroid with 
arterial blood. A section through the choroid and retina (Pl. 
III, fig. 21) shows us that the choroid vessels are arranged in 
suppose that the arterial blood which passes through these filaments receives 
additional oxygen from the water. 
2T have made several separate injections of the ophthalmic artery, cephalad, 
after it leaves the pseudobranchia to see if it had any connection with the other 
arteries, especially the orbitonasal artery with which it comes in such close con- 
tact; but no connection whatever was found. 
