627 
In embryos, the descriptions of this region are much more com- 
plete, this being particularly true of Greir’s recently published and 
excellent work, which I have but just received and the study of which 
has led to the present publication. 
GreIL’s descriptions include embryos from the so-called stage 39 
of Semon’s descriptions to stage 48. In embryos of stages 46—47, 
Grein describes and figures a so-called foramen sphenotrabeculare 
which is said to transmit the vena hypophyseos and the arteria orbi- 
talis. This foramen lies, as its name implies, dorsal to the trabecula, 
between that cartilage and the sphenolateral cartilage, and it is ev- 
idently the homologue of the pituitary foramen of my descriptions of 
selachians fused with the so-called efferent pseudobranchial foramen, 
which latter foramen transmits the dorsal ends of the efferent pseudo- 
branchial and ophthalmica magna arteries fused to form a common 
trunk. Whether the vena hypophyseos of Ceratodus has a cross- 
commissural connection with its fellow of the opposite side or not is 
not stated by Grem, but the vein is shown in one of that author’s 
figures (Fig. 2, Pl.53) running inward immediately posterior to the hypo- 
physis. The pituitary (sphenotrabeculare) foramen lies immediately 
anterior to a foramen, to be described below, that transmits the nervus 
ophthalmicus profundus, nervus abducens and vena pterygoidea (jugular 
vein of my descriptions of other fishes), both of these foramina lying 
at the hind end of the orbit and at the hind end also of a longitu- 
dinally depressed portion of the side wall of the chondrocranium that 
recalls the trigemino-pituitary fossa of selachians. 
In Sewertzorr’s figure giving a lateral view of the chondro- 
cranium of an embryo of stage 47 of this fish, the pituitary foramen 
is apparently faintly indicated, but it is not identified or described 
by him. In Krawerz’s otherwise excellent figures it is also not shown 
as such. There is however in one of Krawetz’s figures (Fig. 7) a 
foramen that is said by him to give exit to the arteria carotis, and 
it is probable that this foramen is the one called by GrEIL the foramen 
sphenotrabeculare. The longitudinal depression in which this latter 
foramen lies is well shown in Krawetz’s, figure and it is said by him 
to lodge the nervus ophthalmicus profundus in its forward course 
through the orbit. 
Posterior to the pituitary foramen there is, in stages 45—46 of 
GreIL’s descriptions, a large space between the hind end of the spheno- 
lateral cartilage and the otic capsule, and it is called by that author 
40* 
