241 
These conditions in selachians can now be compared with those in 
Polyodon, Lepidosteus, Amia, Scomber and Scorpaena, but it must be 
borne in mind that in all these latter fishes the trabeculae are said to 
be laid down, from the very beginning, in the line prolonged of the 
parachordals and not, as in selachians, at first at right angles to those 
cartilages. Because of this, the postclinoid wall appears relatively 
late in the development of both Amia (Auuıs, 1897a) and Lepidosteus 
(Vert, 1911), and doubtless also in all teleosts. 
In Polyodon folium, Brıpez (1879) describes a “short antero- 
posterior canal” the outer wall of which is formed by an oblique “bar 
of cartilage strengthened externally by the basi-temporal wing of the 
parasphenoid’”’; and BRıDGE assumes that the truncus hyoideo-mandib- 
ularis facialis issues by the posterior opening of this canal and the 
ramus palatinus facialis by the anterior opening. This I find to be 
true for the truncus hyoideo-mandibularis facialis but not for the 
ramus palatinus, this latter nerve issuing by an independent foramen 
that lies at some little distance anterior to the anterior opening of the 
short canal. I also find the canal traversed by both the external carotid 
artery and the internal jugular vein, and the latter vein, shortly before 
entering the anterior opening of the canal, receives a pituitary vein 
which issues from the cranial cavity by a special foramen. ‘The con- 
ditions in this fish are accordingly here similar to those in Acanthias. 
The other foramina, fossae and canals are not sufficiently well de- 
scribed by Bridge to warrant reference to them. 
In Lepidosteus osseus the trigemino-facialis chamber and the 
related portions of the pituitary fossa were described independently 
by Vzır (1907) in a 149 mm. specimen and by me in 19mm, 55mm and 
80 mm. specimens and in the adult (Auuıs, 1909; sent to press Feb. 
1907). 
In the 149 mm. specimen Verr shows a space, called by him the 
cavum sacci vasculosi, which he considers as the homologue of the 
myodome (eyemuscle canal) of Amia, but which I considered in my 
specimens as the homologue of the posterior half only of that cavity. 
In my 80 mm. specimen this cavity lodged the saccus vasculosus and 
the median portion of the pituitary vein, it was roofed by membrane 
only, and the tip of the notochord lay slightly posterior to the vein 
in a groove on the dorsal surface of the basis cranu. In the 149 mm. 
specimen Verr finds the cavity still lodging the saccus, but he makes 
no mention of the pituitary vem. The membrane that roofed the 
Anat. Anz. Bd. 46. Aufsiitze. 16 
