THE MYOLOGY OF POLYODON 133 
MM. pharyngoclaviculares: figure 8, m.phg. (1, 2, 3) 
The remaining muscles of this group might be considered as 
one, two or three pairs, depending on the tendency of the writer. 
They all arise in one mass, as in Amia. The fibers destined to 
form the anterior and intermediate muscles take origin from a 
crescentic area just dorsal to the site of origin for the coraco- 
arcualis, with which they are practically continuous. The re- 
maining fibers arise still higher up from the cartilage and from 
the membranous septum that covers the large fontanelle in the 
cartilage. The anterior division is inserted on the anterior part 
of the slender basipharyngeal cartilage and into connective tissue, 
between or actually upon the fifth ceratobranchials. The inter- 
mediate portion is inserted on the basipharyngeal behind the 
foregoing and the posterior part has a similar insertion still 
further back. The latter, however, especially in young fish, is 
not connected closely with the cartilage, but rather with a median 
aponeurosis, the same from which the transversus ventralis takes 
origin. 
Innervation. These muscles are supplied at their common 
origin by branches of the first spinal nerve beyond its anasto- 
mosis with the postvagal nerve. I could trace no branches of 
the vagus into their upper ends. 
Blood supply. WDorsally they are supplied by the a. coraco- 
cardiaca and the posterior dorsal branch of the fourth recurrent 
branchial artery which may show an end-to end anastomosis 
with the former. Ventrally the artery of supply is the infra- 
pericardial branch of the coronary. 
Action. They serve to depress the posterior part of the floor 
of the mouth and assist in the first act in swallowing (?). 
These muscles seem to be entirely lacking in Acipenser sturio 
since Vetter makes no mention of them. They are present in 
Amia, however, and, as McMurrich hints, probably represent 
remains of coraco-arcuales of the fifth, sixth, and possibly seventh 
arch of some ancestral form (cf. Heptanchus). Usually there 
are two of them, the ones referred to above as anterior and 
intermediate being called the ‘external,’ the other the ‘internal.’ 
