ERIK A : SON STENSIO 
The supraorbital canal has its posterior end situated in the middle or posterior 
part of the parietal, from which it passes off anteriorly, entering- the frontal, which it 
pierces in a longitudinal direction. Anteriorly of this bone it looks as if it should enter 
the antorbital, but the part of the sensory canal situated in the latter bone continues 
forward laterally of the nasal aperture, and should most probably belong to the infra¬ 
orbital canal and correspond to the upper end of the infraorbital section of this canal 
(Allis 1905, p. 491; cf. also Allis 1919 a, p. 375). This view is also supported by the 
fact that this part of the sensory canal presumably communicated with the infraorbital 
canal, as is the case in the closely related Catopterids (cf. text figs. 80, 81, 85, 86). If 
this is correct, the most anterior part of each supraorbital canal must of course be 
reduced or else have a pit-line on the nasalo-postrostral corresponding to it. 
The infraorbital canal forms, as usual, a direct anterior continuation of the cranial 
section of the main lateral canal. It runs forward through the anterior part of the supra- 
temporo-intertemporal and from this bone enters the dermosphenotic with a gradual bend 
to the lateral side. From the dermosphenotic it probably entered the infraorbitals, in 
which it continued first downwards and then forwards. No further details of its course 
in these bones are, however, known. No anastomosis is developed between its posterior 
part and the supraorbital canal, as in Teleosts, recent higher ganoids, and sturgeons. 
Of the preopercular canal only the dorsal end has been observed so far (Boreoso- 
mus), and this end is situated in the supratemporo-intertemporal, where it anastomises 
with the infraorbital canal and the cranial section of the main lateral canal at the place 
where these two pass over into each other. In its downward course it may have entered 
the preoperculum, where, as far as we can judge from the conditions in the closely 
allied Catopterids, it ought to have been situated fairly close to the posterior margin. It 
is not known whether it anastomised with the mandibular canal. 
I hav distinctly observed the mandibular canal in a number of forms. It is situated 
rather near the posterior and ventral margins of the mandible and pierces both the an¬ 
gular and the dentalo-splenial. 
The cranial section of the main lateral canal of the body extends through the 
lateral extrascapular or the lateral part of the extrascapular plate (if only a large paired 
plate is present on each side of the median line) into the supratemporo-intertemporal, 
where, as has been mentioned, it is continued without interruption by the infraorbital 
canal. Between the cranial sections of the right and left sides there is a distinctly developed 
supratemporal commissure, situated in the usual way in the extrascapulars (Boreosomus; 
Elonichthys , Traquair 1901, p. 83). 
Only one head line of pit organs could be observed (Boreosomus). This one, which 
is situated on the parietal, is rather short and is situated transversally in relation to the 
axis of length of the head and seems to correspond to the middle one of the three 
lines of pit organs found in Amia and many recent Teleosts. Nothing is known as yet 
with regard to cheek lines of pit organs. 
Axial skeleton. 
The chorda dorsalis has been well developed and does not seem to have been 
affected to any noticeable extent by the formation of vertebral bodies. 
