629 
and KRAWETZ the processus palatobasalis, and it is quite certainly the 
homologue of the processus basalis of my descriptions (1914a) of 
selachians and not of the so-called palatobasal (orbital, ALLIs) process 
of those fishes. 
In stages 45—46, GrEIL shows (Figs. 21, 22, Pl. 61) the united 
body and articular process of the palatoquadrate projecting postero- 
laterally, and from the proximal half of its length, approximately, a 
stout wide bar of cartilage projects dorso-posteriorly and is called by 
him the pars ascendens of the processus anterior of the palatoquadrate. 
It is said (p. 1136) to fill the space between the root of the trabecula 
and the wall of the labyrinth, and it is shown in the figures extend- 
ing dorso-posteriorly across the incisura sphenotica, its dorso-posterior 
end, which is called the processus oticus, fusing with the cartilage 
of the otic capsule at its dorso-anterior end. 
In SEWERTZOFF’s figure of an embryo of stage 46, this pars 
ascendens of the palatoquadrate is not even indicated, but as, in this 
embryo, the otic capsules also have not yet undergone chondrification, 
the embryo unquestionably represents an earlier stage in the devel- 
opment of the chondrocranium than the embryo of stage 45 figured 
by Grem. This early embryo of Ceratodus thus shows definitely that 
the pars ascendens of the palatoquadrate develops later than its ventral 
portion, a fact that is certainly of importance and that will be later 
again referred to. 
When the pars ascendens of the palatoquadrate has developed, 
it forms, as shown in GREIL’S figures, a bridge across the incisura 
sphenotica, and as this bridge is somewhat arched there is a space 
left between it and the plane of the incisure, and as I shall show 
that this space is the trigemino-facialis chamber of the fish it will 
facilitate the descriptions to so call it at once. 
The trigemino-facialis chamber, as above defined, has, in this 
stage 45—46, two large openings which lead to the external surface 
of the chondrocranium. The anterior one of these two openings is 
apparently called by GreiL the foramen sphenoticum commune, but 
there is some confusion in the terms applied to it. The posterior 
opening is first called by him (p. 1123) the foramen praeoticum basi- 
craniale, and he says of it: “Durch die Wurzelspange des Palato- 
quadratums wird nun diese Incisura (sphenotica) nach aussen über- 
brückt und zum Foramen basicraniale gemacht.” This is wholly in- 
correct, for the incisure is a primary perforation of the cranial wall 
