643 
and ophthalmica magna arteries are practically continuous, as they 
are in teleosts, and that they fall into the internal carotid artery as 
that artery is traversing a canal in the lateral wall of the chondro- 
cranium; that canal apparently lying dorsal to the trabecula, though 
my specimens are all too old to permit of this being definitely determ- 
ined. In this fish there is no arteria orbito-nasalis, and I now find, in 
re-examining my sections, a smal! branch of the arteria optica that runs 
forward to the nasal sac, lying, in its course, partly in the cartilage 
and partly between the cartilage and the lining membrane of the 
cranial cavity. A branch of this artery is sent to the orbit with the 
nervus trochlearis, supplying the musculus obliquus superior, and in 
the nasal fossa the artery runs into and is continuous with a terminal 
branch of the orbital, or maxillary (ALLEN) branch of the carotis externa, 
In the adult Amia (Auruıs, 1912) the fused dorsal ends of the 
efferent pseudobranchial (mandibular) and ophthalmica magna (pre- 
mandibular) arteries traverse a canal in the presphenoid bolster and 
fall into the internal carotid artery while that artery is traversing 
the same cartilage; aud as this presphenoid cartilage seems unques- 
tionably to be of trabecular origin, the chondrification of the trabeculae 
has here been so related to the cranial flexure that the dorsal ends 
of the united mandibular and premandibular aortic arches have been 
enveloped in the forming cartilage and so enclosed in a canal that 
traverses it, instead of passing dorsal to it, to reach the aorta. As 
in Polyodon, there is no arteria orbito-nasalis, and I have shown in. 
my figure of the arteries of this fish (ALLIS, 1912, p. 129) a branch 
of the arteria cerebralis anterior which runs forward into the nasal 
fossa and there runs into and is continuous with a branch of the 
opthalmicus branch of the carotis externa. 
In Lepidosteus (Auuıs, 1909), the efferent pseudobranchial artery 
joins the internal carotid ventral to the chondrocranium, as it does 
in teleosts, the latter artery then running upward internal to the 
trabecula and immediately giving off a small branch which issued, 
in my specimens, with the nervus opticus. This small artery I consid- 
ered at the time as possibly a persisting remnant of the arteria 
ophthalmica magna of other fishes, a conclusion which I now consider 
to be confirmed; this artery in Lepidosteus thus running dorsal to 
the trabecula. The chondrification of the trabeculae must accordingly 
here have been so related to the cranial flexure that each trabecula 
crossed the related lateral dorsal aorta at a point that lies between 
41* 
