VISCERAL ARCHES OF THE GNATHOSTOME FISHES. 357 
those fishes make it certain that the conditions were there 
considered by him to be similar to those in Amia. In Poly p- 
terus senegalus the musculi pharyngoclaviculares are said 
to be developed as in Amia, but from the ventral end of the 
fourth instead of the fifth myotome. 
Regarding the innervation of the coracobranchiales, Edge- 
worth says (loc. cit., p. 253) : “ A. coraco-branchialis, or 
pharyngoclavicularis externusandinternus, developed by back- 
ward growth from the last branchial myotome, i. e. fourth in 
Polypterus senegalus, fifth in Amia, Salmo, Menidia, 
may either retain its original branchial innervation from the 
tenth, e.g. Amia (Allis), Esox (Yetter), Menidia (Herrick), 
Lepidosteus, Polypterus senegalus, or be innervated by 
spino- occipital nerves, e.g. Amiurus (Wright), Salmo 
(Harrison). When coraco-branchiales are developed from 
all the branchial myotomes, they are innervated by the 
spino-occipital nerves, e.g. Selachii (Yetter, Furbringer), 
Acipenser (Yetter), Polypterus ? species (Furbringer), Cera- 
todus (Furbringer) Y 
Certain of the musculi coracobranchiales are thus, like the 
trapezius, muscles said by Edgeworth to be innervated by the 
nerve of a segment of the body other than that from which 
the muscle is derived. The muscles said by him to be inner- 
vated by the nervus vagus can be left out of account in this 
respect, and the muscles in the Selachii, and the tendons that 
are said to represent the muscles in Acipenser, have been 
already considered. In Ceratodus, the dorsocleidobrancliialis 
of GreiFs (1913) descriptions, from which the so-called coraco- 
branchialis is said to be developed, is said by that author to 
be innervated, in embryos, by the nervus vagus, and although 
Furbringer (189?), who is quoted by Edgeworth, includes 
this muscle of this fish in the hypocranial spinal muscles, 
innervated by spino-occipital nerves, I cannot find that he 
himself traced their innervation by branches of those nerves. 
In Ameiurus, Herrick (1901, p. 209) says that the pharyngo- 
claviculares are innervated by the vagus, and not by spinal 
nerves as they were said to be by Wright, and I have con- 
