ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 765 
the ventral or external boundary of the second fenestra, to constitute the dorsal 
boundary of the third fenestra, and to fuse behind with the hyoid arch as above 
described. Both the above processes consist entirely of hard cartilage. The third or 
mferior process forms the ventral boundary of the third fenestra, and fuses behind 
with the hyoid arch. It exhibits at about the middle of its course a conspicuous zone 
of soft cartilage absent in Bdellostoma, according to Parkkr, and is in fact more or 
less generally invaded by nests of soft cartilage. Its posterior upper inner surface 
receives the rod of soft cartilage from the external lateral velar bar, as elsewhere 
described. The pterygo-quadrate, lying nearer the surface, takes no part in the 
skeletal support of the pharynx, except to a slight extent the inferior process. 
“ Palatine” Bar (figs. 1 and 2, pl.).—Forms with the above the palato-pterygo- 
quadrate of Ayers and Jackson, and commences behind by a wide stout base of soft 
eartilage fused with the trabecula and anterior process of the pterygo-quadrate, as 
above described. It then passes forwards and somewhat inwards, lying at the lateral 
margin of the ventral wall of the cranium and nasal capsule, to expand in front and 
to fuse, as the palatine commissure, with its fellow of the opposite side at the level 
of the anterior border of the nasal capsule. The commissure is a wide thickish bar 
of hard cartilage, and somewhat arched, with the convexity dorsal. Into the ventral 
concavity fits the base of the median dorsal tooth. Parker figures an anterior 
“ethmoid” tract of soft cartilage in the commissure, and I also find some evidence 
of this in my sections. The cornual cartilage fuses irregularly with the external angle 
of the commissure, and where this occurs there is an invasion of the hard cartilage by 
nests of soft cartilage. Ayers and Jackson state that in Bdellostoma the cornual 
cartilage is ‘‘attached” to the palatine, and I take it this does not mean fusion. 
Immediately in front of the palatine commissure and the median dorsal tooth a 
median pad, consisting of soft pseudo-cartilage, is seen, which passes forwards over the 
roof of the pharynx for a short distance. It is invaded, especially in front, by several 
nests of true soft cartilage. Anteriorly, it lies between the diverging palato-ethmoidalis 
profundus muscles, with which it is very closely connected. Its true relations are 
shown in vertical longitudinal sections, when it is seen to arise from the anterior 
border of the base of the median dorsal tooth, pass forwards for a short distance, and 
then curve backwards round the anterior margin of the palatine commissure to be 
inserted into the posterior extremity of the subnasal bar. Only the former part 
consists of pscudo-cartilage. I shall refer to it again in my next part on the muscles. 
In the meantime I need only point out that it corresponds to the occurrence of soft 
pseudo-cartilage in the tendons of other muscles, such as those of the “lingual” 
apparatus, as described elsewhere. 
Cornual Cartilage (figs. 1 and 2, c. c.).—Fuses behind, as above described, with the 
palatine commissure, and consists of soft cartilage. It passes forwards and outwards in a 
curve immediately internal to the M. tentacularis posterior, its anterior free extremity 
coursing parallel and just external to the lateral labial cartilage. In the sections the 
TRANS, ROY. SOC. EDIN., VOL. XLI. PART III. (NO. 30). 113 
