The Development of the Cartilaginous Skull ete. in Necturus. 425 
and connects the auditory capsule with the trabecular part of the 
basal plate. The posterior bar arises from the region which Srönr 
(80) calls the »mesotie« part of the basal plate, and fuses with the 
auditory capsule at its inner, posterior margin. The relations of 
this bar of cartilage will be further discussed in connection with 
the description of the chondrocranium in Necturus 46 mm long. 
Fig. 28, pl. XVIII, shows a transverse section through the anterior 
bar. Gradually the space between the two connecting bars closes, 
and the floor of the auditory capsule becomes throughout continuous 
with that of the basal plate. Meanwhile a second connection 
between the trabeculae and the auditory capsule appears anterior 
to the facial ganglion, so that the rami hyomandibularis and 
palatinus then pass outwards through foramina in the floor of 
the skull. 
When chondrification takes place in the basicranial plate, the 
prochondral tissue is gradually transformed into cartilage, the clear 
matrix of which is first found in the mesodermic part of the trabe- 
cular bars, and extends thence both forwards and backwards, leaving, 
however, the triangular area which surrounds the point of the chorda 
unchondrified (fig. 14). While this anterior region of chondrification 
is extending backwards through the procartilage of the basicranial 
plate, a second paired area of chondrification appears in the occipital 
region, where the clear matrix of cartilage is also soon found. These 
posterior centres of chondrification lie at the base of the occipital 
arch in the same horizontal plane as the chorda, although not in 
immediate contact with the chorda. 
The paired Anlagen of the anterior and posterior regions of the 
head, are at no time sharply limited towards one another, but each 
passes gradually into the intervening procartilage of the basicranial 
plate which soon chondrifies in its median part in continuity with 
both anterior and posterior areas of chondrification. There is conse- 
quently an intermediate area in the plate where chondrification 
takes place slightly later than near the two extremities, but two 
pairs of distinct cartilages, the homologues respectively of the »Bal- 
kenplatten« and »Oceipitalplatten«, described by Sréur ('88) in 
Triton, are not found in Necturus. 
Although the procartilage of the basicranial plate is deeper in 
those transverse sections which pass near the point of the chorda 
and in those through the occipital region, than in the intermediate 
Space, as seen by comparing figs. 7 6, 7 d, and 7 e with fig. 7 e, 
