854 
EDWARD PHELPS ALLIS. 
coexist, in Heptanchus, Scyllium, and Mustelus, with the 
coracobranchiales and are inserted on them, but form no 
part of them. The coracobranchiales would then not be 
derived in any part from branchial myotonies, and their 
primitive innervation would depend upon what nerve or 
nerves innervated the parts of the pericardial wall from 
which they were derived, and this might evidently be either 
by branchial or postbranchial nerves. But if these muscles 
and the coracomandibularis are both derived from cells of 
similar origin, as van Wijhe states, and if the coraco- 
mandibularis was primarily innervated by spinal or spino- 
occipital nerves, the coracobranchiales must certainly also 
have been so innervated, and even Edgeworth does not 
question that the coracomandibularis was primarily as well 
as actually innervated by those nerves. Edgeworth further- 
more says (loc. cit., p. 178) that no muscles are directly formed 
from the walls of the branchial portion of the cephalic 
coelom, which, if correct, would indicate that the muscles 
described by van Wijhe were developed in the postbranchial, 
or spinal, region. The anatomical evidence is also all strongly 
in favour of the similarity of origin of these muscles ascribed 
to them by van Wijhe, and until the conflicting embryo- 
logical evidence has been controlled it accordingly seems 
proper to conclude that all the so-called hypobranchial 
muscles are of similar origin, and that they were primarily, 
as they are actually, innervated by spinal or spino-occipital 
nerves. 
In Chimaera coracobranchiales are said by Vetter (1878) 
to be found, and to there closely resemble the muscles found 
in the Selacliii. These muscles are thus found in all the 
Elasmobranchii, and in all of these fishes they are said to be 
innervated by spinal or spino-occipital nerves. 
In the Teleostomi and Dipneusti, coracobranchiales have 
been described as such in certain fishes, while, in other 
fishes, muscles described under other names are said to be the 
homologues of the coracobranchiales of the Elasmobranchii. 
In Acipenser the coracobranchiales of the first three 
