628 
the incisura sphenotica. The ventral portion of this incisure is said 
to lie between otic and preotic portions of the parachordal cartilage, 
and the sphenolateral cartilage is said to arise from the preotie portion 
alone, no limiting line between the two cartilages being however shown 
by Gremt, or by SEWERIZOFF in his figures of this same stage. In 
stages 47—48, a bar of cartilage, which is called by Grein both the 
pons sphenoticus and the pons sphenoticus superior, extends from the 
dorso-posterior corner of the sphenolateral cartilage to the otic capsule, 
bridging the dorsal edge of the incisura sphenotica and making of 
this incisure a closed foramen in the lateral wall of the chondro- 
cranium. The large foramen so-formed is first called by Grem the 
foramen praeoticum laterale sive sphenoticum (p. 1238), but is later 
also called the foramen prooticum laterale (p. 1864), or simply the 
foramen prooticum or the foramen sphenoticum. It is a simple fenes- 
tration of the lateral wall of the chondrocranium, and it is said to 
give passage to the nervus abducens and to the roots and ganglia of 
the trigemino-facialis complex; but it apparently also gives passage to 
the vena cerebri media (see Grem’s Fig. 3, Pl. 53), Grum’s statement 
(p. 1260) that this vein traverses the foramen sphenoticum majus 
being probably due to a misconception of the latter foramen, as will 
be later explained. As the foramen prooticum laterale is also said 
by Grein (p. 1123) to lodge the acusticus ganglion, it is evidently 
the homologue of the cerebral opening of the acustico-trigemino-facialis 
recess of my description of certain selachians (Atus, 1914b), and 
the fact that it lodges this acusticus ganglion would seem to clearly 
indicate that the plane of the incisure corresponds to the mesial and 
not to the lateral wall of the recess of selachians. The lateral wall 
of the recess is then not only wholly wanting but not even indicated 
in these embryos of Ceratodus. 
The trabeculae are said by Grein (pp. 1136 and 1156) to arise 
independently of the parachordals and to be continued posteriorly in 
the so-called processus anterior sive trabecularis of the palatoquadrate 
of either side; and these two parts of a single continuous cartilage 
are said by Grem to fuse, at their point of union and by their mesial 
surfaces, with the lateral surface of the preotic portion of the para- 
chordal cartilage. It is not said by Grem that the processus anterior 
palatoquadrati is primarily independent of the trabecula, but SEwER- 
1zorr definitely states this to be the case. The processus anterior 
palatoquadrati of GrREIL’s descriptions is called by both SEWERTZOFF 
