HYOMANDIBULA OF THE GNATHOSTOME FISHES 603 
not yet been segmented off from the dorsal ends of the cerato- 
branchials. The pharyngobranchials, as thus determined, lie an- 
terior to the efferent arteries of their respective arches, instead of 
posterior, as in the several Plagiostomi that I have examined in 
connection with this work, and they each articulate with the dor- 
sal end of the related epibranchial instead of with the posterior 
edge of that end, as in the Plagiostomi; Ceratodus possibly rep- 
resenting, in this respect, an intermediate stage between the 
plagiostome and teleostome conditions. 
In an embryo of Stage 48, Greil shows (l.¢., fig. 548, p. 1397) 
two of the so-called epihyal or hyomandibular cartilages, and he 
says that there may even be three of them. The two cartilages 
shown in his figure 543 form a curved line which extends from 
beneath the auditory capsule nearly to the dorsal end of the cera- 
tohyal; and the nervus hyomandibularis facialis runs outward 
and downward immediately external to them both, this doubt- 
less being the relation of the nerve to the third cartilage also, 
when present. The dorsal one of these two or three cartilages is 
certainly the hyomandibula (Ph) of Greil’s descriptions of earlier 
stages, and it does not reach, by an appreciable distance, the 
wall of the auditory capsule, this embryo of Stage 48 thus being 
less advanced in this respect than Krawetz’s embryo of Stage 
47/48. The vena jugularis lies dorsal to the dorsal end of the 
cartilage, and the arteria carotis interna (lateral dorsal aorta) 
ventro-mesial to it. The second cartilage shown in Greil’s figure 
corresponds closely to the symplectic (Hx) of Krawetz’s figure 
20, of an embryo slightly older than Stage 47, and is quite cer- 
tainly that cartilage notwithstanding that it does not, in this 
embryo of Stage 48, extend upward to the processus oticus palato- 
quadrati; Greil’s embryo here again representing a less advanced 
stage of development than Krawetz’s younger embryos. The 
third cartilage may be called the cartilage Eh. These two or 
three little cartilages are said to form the entire dorsal half of 
the cartilaginous bar of the hyal arch, and, as Greil calls them all 
epihyal or hyomandibular cartilages, it seems certain that the 
term epihyal is used in the sense of epi-pharyngohyal and that he 
considered the several cartilages to represent, together, the se- 
