TRIASSIC FISHES FROM SPITSBERGEN 
263 
The infraorbital canal of either side (ifc, text figs. 80, 81; Pl. 84, fig. 1) is, as usual, 
connected posteriorly with the anterior end of the cranial section of the lateral canal 
in the supratemporo-intratemporal. It passes off forward through this bone with a gra¬ 
dual bend to the lateral side and has then presumably entered the dermosphenotic, where 
it is not, however, preserved. In its further course downwards and forwards it first 
pierces the infraorbitals behind and beneath the orbital entrance, then entering the 
rostral. In this bone it has, if the view just put forward by me above is correct, been 
so ramified that one branch passed off upward and backward through the antorbital, 
while the other continued forward and medially, entering the nasalo-postrostral, where 
it formed an ethmoidal commissure with that of the opposite side. This commissure 
forms a deep sinus backwards within the nasalo-postrostral ( ethm. com, text fig. 80; 
PI. 34, figs, x, 2). 
On the commissural section of the infraorbital canal from the place of communi¬ 
cation with the suborbital section in the rostral plate to the place where it meets that 
of the opposite side in the median line, 5—6 foramina for nerve branches to the sen¬ 
sory organs could be' observed. On the canal portion in the antorbital there are about 
number of these foramina. 
The preopercular canal ( poc, text fig. 81; PI. 34, fig. 1) is situated quite close to 
the posterior margin of the preoperculum and on this margin numerous exceedingly 
small tubuli have their openings. It was impossible to observe whether it communicated 
with the mandibular canal and the canal in the supratemporo-intertemporal. 
The mandibular canal (text fig. 81) runs as usual through the mandible in the 
the same neighbourhood of its posterior and lower margins. 
The cranial section of the main lateral canal (text figs. 80, 81; PI. 34, fig. 1) had its 
course from its anterior end in the supratemporo-intertemporal backwards through that 
bone, then piercing the lateral part of the extrascapular. Between this section of the 
sensory canal on the right and left sides there is a supratemporal commissure, situated 
in the extrascapulars ( s . com, PI. 34, fig. 1). . 
An anterior «head-line of pit-organs» ( ap, PI. 34, fig. 1) is described above in con¬ 
nection with the description of the supraorbital canal, of which it formed a direct posterior 
Continuation. In addition, however, a middle and a posterior head-line are found, each 
represented by a rather short furrow on the parietal. The posterior head-line ( pp, PI. 34, 
fig. 1), which issues from the- posterior margin of. the parietal, runs first anteriorly for a 
short way and then bends off antero-medially. The middle head-line (mp, PI. 34, fig. 1), 
which begins between the posterior and the anterior one, passes off laterally and some¬ 
what anteriorly (cf. text figs. 8o, 81). 
It cannot be established with certainty whether «cheek lines* of pit-organs were 
present or not. 
The skeleton of the unpaired fins. 
The anal fin (A, PL 28, fig. 3 ; Pl. 33 ; PL 35, fig§. 1, 3 ) is rather small and is situated 
fairly far back. It is triangular in shape with its base and height almost of equal size. 
The ganoine-covered lepidotrichia number about 10, all of which are unjointed for a 
-comparatively long distance proximally. Otherwise they are closely jointed and even 
-dichotomically ramified distally. The fulcra are numerous and strong. 
