VISCERAL ARCHES OF THE GNATHOSTOME FISHES. 377 
constrictores superficiales had entirely disappeared in the 
Teleostei, but as, as I have fully explained in preceding pa ges, 
Vetter’s descriptions of these muscles are not wholly correct,, 
my deductions from them were also not wholly correct. In a 
recent work (Allis, 1915), still influenced by Vetter’s descrip- 
tions, I suggested that the adductor hyomandibularis of the 
Teleostei might be the homologue of the inferior postspiracular 
ligament of the Selachii ; but as the adductor hyomandibularis 
of the Teleostomi would then be the serial homologue of tlio 
adductores arcuum branchialium of the Selachii, this cannot 
be if my present conclusions are correct. 
Edgeworth (l.c., p. 210) says that the retractor hyo- 
mandibularis of Acipenser, and the adductor hyomandibularis 
of Lepidosteus, Ami a, and Sal mo, are all derived from the 
anterior portion of the constrictor superficialis of the liyal 
arch of the Selachii, and that the musculus opercularis of 
Acipenser and Lepidosteus, and the adductor and levator 
operculi of Amia and Salmo, are derived from the posterior 
portion of that constrictor of the Selachii ; which is in accord 
with my present conclusions. The levatores arcuum branchi- 
alium of the Teleostei are said by Edgeworth to be developed 
from the upper ends of the branchial myotomes, which i& 
evidently correct, but he then further says that, because of 
this origin, these muscles of the 'Teleostei have no counter- 
parts in the Selachii, unless it be in the musculus trapezius as 
described by him, which I consider incorrect. 
The proximal (anterior) fibres of the ventral portion of the 
constrictor superficialis of the hyal arch must, primarily,, 
have nil been inserted on the ceratohyal, and, in the Selachii, 
they became connected with their fellows of the opposite 
side by a median ventral aponeurosis, and so formed a musculus 
interhyoideus which extended from one hyal arch to the 
other across the ventral surface of the head. But a more or 
less important portion of the fibres later here acquired, as in 
the dorsal portion of the constrictor, a secondary insertion on 
the mandibular cartilage of either side, and so became an 
