356 
KD WAR'D PHKLPS ALUS. 
strictores superficiales of Heptanchus, Scyllium, and Mustelus, 
and not the homologues of -the hypobranchial coracobran- 
chiales of those fishes. The' musculus coracoarcualis posterior 
of Acipenser, if its innervation by spinal nerves is correct, 
might - be. the homologue of the coracobrancliiales of the 
Selacliii, but this innervation needs confirmation. 
In Ceratodus, coracobrancliiales are said by Edgeworth to 
be developed from the ventral ends of the second, third, and 
fifth branchial myotonies, but not from those ends of the first 
and fourth myotonies. In later stages, still another coraco- 
branchialis is said to be differentiated from the already 
differentiated interarcualis ventralis of the first branchial 
arch. Greil gives quite a different account of the origin of 
these muscles. According to him (1913) there is but one 
coracobranchialis on either side of the head of this fish, and 
it is said, as already explained, to be developed from the 
external one of two processes of the ventral end of the axial 
mesoderm of the fifth branchial arch, that mesoderm being 
derived from a ventral process of the second trunk myotome. 
The muscle is said by Greil (loc. cit. , p. 1344) to grow forward 
and separate into three or four heads which acquire insertions 
on the ventral ends of the branchial bars. The ventral ends 
of the axial mesoderms of the first to the fourth branchial 
arches are said to develop, respectively, into the musculi 
ceratohyoideus, interbianchialis anterior, interbranchialis 
posterior, and interbranchialis IV, while from the deeper 
one of the two processes from the ventral end of the axial 
mesoderm of the fifth arch the dorsopharyngeus is said to be 
developed ; all of these muscles being said to be serial homo- 
logues one of the other and all wholly independent of the 
coracobranchialis. 
In Amia, Edgeworth says (loc. cit., p. 237) that only one 
coracobranchialis is developed, the coracobranchialis V, and 
this muscle, in 14 mm. embryos, is said to divide into the 
pharyngoclaviculares externus and interims of the adult. In 
the Teleostei the development of these muscles is not par- 
ticularly described, but references made by Edgeworth to 
