182 
ERIK A : SON STENSIO 
In sturgeons the supratemporo-intertemporal has a lamella that closely resembles 
the one (vp) in B. mougeoti, though it has not the long forward, downward and medially 
directed process, and Sagemehl (1884, foot-note pp. 188—189) also describes a rather 
similar one in Amia. In Coelacanthids too, as is shown by my description in this work 
(pp. 63 , 81, 96 above), I found a lamella in a similar position, issuing from the supratemporal 
part of the supratemporo-extrascapular and the intertemporal part of the parieto-inter- 
temporal. In addition the Coelacanthids have on the supratemporo-extrascapular, as we 
have seen, a process (h) that, at least at a hasty inspection, appears to have about the 
same conditions as the process vp in B. mougeoti. If, however, n. facialis in Coelacanthids 
has had its exit from the cranial cavity in front of the process f,, as I consider most 
probable at present (cf. p. 60), the process h in them would be situated somewhat caudally 
of the process vp in B. mougeoti. If, on the other hand, n. facialis in Coelacanthids has 
had its exit behind the process f h the two processes in question here might possibly be 
homologous. 
As we shall see from the following description (part. II), in Saurichthyids too 
there seems to be a certain correspondence to the process vp in B. mougeoti. 
The relation we found in B. mougeoti between the supratemporo-intertemporal and 
the prootico-opisthotic is noteworthy from another point of view as well. For the 
fixation between the supratemporo-intertemporal and the primordial neurocranium that 
has arisen in this case seems to afford us an idea as to how the pterotic was developed 
in Teleosts and of the homologue of the cartilaginous bone component in this bone 
(cf. pp. 154—161 above; cf. also Sagemehl 1884, foot-note pp. 188—189). 
For if we assume that the prootico-opisthotic, for instance, extended farther 
forward on the dorsal side of the posterior exit of the facialis canal, it would, at least 
partly, have surrounded the process vp, so that the supratemporo-intertemporal would 
have obtained a very fixed connection with the primordial neurocranium. From a stage 
of this sort a fusion between the prootico-opisthotic and the supratemporo-intertemporal 
can easily be thought to have arisen, and if this is so, then finally, owing to the 
influence of musculus constrictor superficialis 2 or muscles derived from this (cf. Vetter 
1878; Ruge 1897), the supratemporo-intertemporal together with a dorsal part of the 
prootico-opisthotic would have been broken loose from the other parts of the prootico- 
opisthotic. This dorsal part of the prootico-opisthotic would form about the dorsal half 
of an opisthotic. The cartilaginous bone component in the pterotic would thus, as I have 
tried to show above, be homologous with the dorsal part of the opisthotic. 
With regard to the membrane bones of the cranial roof in B. mougeoti it ought finally to 
be noted that, as far as one can judge, they rest close against the dorsal surface of the 
primordial neurocranium and that apparently no muscle fossae have been developed beneath 
them. Above the anterior part of the labyrinth region the frontals are broken off and some¬ 
what pressed down into the cranial cavity (see PI. 24, fig. 2), which may perhaps indicate 
that a fontanel had been situated at this place as in Saurichthys ornatus (cf. PartII)i 
Visceral skeleton. 
Specimen P. iyi has several elements of the visceral skeleton well preserved. The 
account given here is entirely based on this specimen. 
