TRIASSIC FISHES FROM SPITZBERGEN 
181 
The membrane bones of the cranial roof. — The cranial roof in B. mougeoti 
(PI. 24, fig. 2) as far as it is preserved, seems to show on the whole Palaeoniscid-like 
conditions. One can identify the paired frontal (Fr, PI. 24, fig. 2), dermosphenotic (der¬ 
mal postfrontal, Dsph, PI. 24, fig. 2), supratemporo-intertemporal («squamosal», Stemp. it, 
PI. 24, fig. 2) and probably the parietal (Pa), and a supraorbital (So) as well. All these 
bones are, however, only fragmentarily preserved and their bone substance is to a great 
extent quite weathered away, so that in most cases only impressions of the lower side 
are left. Some of them are also partly much broken. It is not possible under these 
conditions to fix quite acurately in details the course of the sutures between them. 
The frontals are long and relatively narrow. Their posterior end is situated above 
the anterior half of the labyrinth region. Their anterior one is not preserved but must have 
extended on to the ethmoidal region. The centres of ossification are above the posterior 
half of the partes laterales of the sphenoid. Medially they meet each other in the 
normal way, and the suture between them was probably fairly straight. 
The dermosphenotic is a rather large bone, on either side of the cranial roof, with 
its centre of ossification over the anterior part of the autosphenotic. Its lateral and 
rostral extensions cannot be established. 
The parietals, normally situated above the posterior part of the labyrinth region, 
are presumably represented merely by the anterior ends. 
The supratemporo-intertemporal of either side seems to have been a large and 
rather wide bone extendig forward as far as over the most posterior part of the orbit, 
where it meets the dermosphenotic in the usual way. Medially it was bounded by the 
frontal and parietal. A considerable posterior portion of it is not preserved, and its 
extension backwards cannot therefore be established. The centre of ossification is not 
preserved either, but, to judge from the radiation of the bone substance, it was probably 
above the lateral edge of the prootico-opisthotic, fairly far back. A line drawn between 
the ossification centres of the two supratemporo-intertemporals would in its middle part 
have almost coincided with the suture between the parietals and frontals. 
Each supratemporo-intertemporal extended laterally out past the lateral edge of 
the primordial cranium, but it is impossible to ascertain how far. On the ventral side 
there issues from each of them a perpendicular, long, but not especially high lamella 
(pi, text figs. 60, 61, 64B) which is closely actual in its posterior part to the upper part 
of the lateral surface of the prootico-opisthotic. The anterior and larger part of this 
ventral lamella, however, has rested against cartilage and reaches forward nearly to 
the posterior end of the autosphenotic. 
From the posterior part of this lamella there issues in a forward, downward and 
medial direction a long process (vp, Pl. 22, fig. 3 ) which in the present state of pre¬ 
servation is somewhat broken and squeezed in the gap between the prootico-opisthotic 
and the processus ascendens of the parasphenoid. It is evident, however, that this process 
cannot be much displaced from its original position, at its ventral end must, on account 
of its shape, have helped to form the dorsal boundary of the posterior exit of the facialis 
canal. It ought therefore to have beeri situated in about the way shown in text fig. 61 (vp). 
As it was rather thick it must of course have been sunk in cartilage to some extend. Its 
posterior edge was situated close against the anterior margin of the prootico-opisthotic. 
