TRIASSIC FISHES FROM SPITZBERGEN 
217 
The sculpture on the opercular bones and the radii branchiostegi is comparatively 
fine and consists of numerous tubercles, which are somewhat prolonged in the longitu¬ 
dinal direction of the fish. The posterior part of the maxillary also has a similar sculp¬ 
ture. On the anterior part of the same bone, on the contrary, the tubercles become 
longer and coarser so that they might really be called short striae, and in addition it is 
to be noted that they are not situated quite horizontally, but are directed somewhat 
forwards and downwards. The jugular plate has at its anterior part a rather well 
developed longitudinal striation, while farther backward sculpture is lacking except on 
a median part which has a weak tuberculation. The mandible is relatively coarsely 
ornamented with numerous, densely placed striae and tubercles, the latter forming a 
row along the labial margin; the striae, on the other hand, apart from the rather long 
ones situated farthest posteriorly, are otten somewhat undulating and arranged so that 
as a rule, they run not quite horizontally but with a slope downwards and backwards. 
The sensory canals of'the head. 
The sensory canals of the head are incompletely preserved. They are fine and, as 
far as can be judged, seem to show the usual conditions. Apart from possible «pit-lines» 
they are quite enclosed in bone. 
The supraorbital canal ( soc, PI. 27, fig. 3 ) may have had its course backwards and 
somewhat medially through the frontal, continuing farther backwards into the parietal, 
where it extended almost close to the posterior margin. 
The infraorbital canal (ifc, PI. 27, fig'. 3 ) forms, as usual, a direct anterior con¬ 
tinuation of the cranial division of the lateral canal. Passing off in a forward direction 
it pierces the intertemporal component of the supratemporo-intertemporal and from there 
enters the dermosphenotic. In the latter bone it turns laterally and downwards, leaving 
the cranial roof and passing over to the cheek. As far as can be seen there was no 
anastomosis between its posterior portion and the supraorbital canal. 
The preopercular canal ( poc , PI. 27, fig. 3 ) enters with its dorsal end into the supra¬ 
temporo-intertemporal and there communicates with the infraorbital canal and the cranial 
division of the lateral canal at about the place where these pass into each other. Further 
details of its course are not known. 
The cranial section of the main lateral line of the body (/, PI. 27, fig. 3 ) is only 
preserved in its anterior part; which is situated in the supratemporal component of the 
supratemporo-intertemporal. It is obvious, however, that, in spite of this, it must have 
pierced the lateral part of the large extrascapular, then continuing through the supra¬ 
scapular. The supratemporal commissure can be distinctly shown ( s. com, PI. 27, fig. 3 ) 
and is, as usual, situated in the extrascapulars. 
On the lower wall of that part of the cranial division of the lateral canal that is 
situated in the supratemporal component of the supratemporo-intertemporale there are 
two small foramina, each of which probably transmitted a nerve branch for a sensory 
organ (cf. Allis 1889, PI. XLII; 1900a, b; 1905; Cole 1898, PI. 22 etc.). Each of the 
foramina in question has a tubulus corresponding to it and this tubulus issues in a 
lateral direction and opens on the dorsal surface of the supratemporo-intertemporal near 
the lateral margin. 
Stensio, Triassic Fisfies from Spitzbergen. 28 
