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ERIK A : SON STENSIO 
basisphenoid. Only Macropoma seems, as far as is known, to be different, inasmuch as in 
this species the fronto-dermosphenotics are possibly subdivided into two parts, an anterior 
and a posterior one, the former of which is the longer. The fronto-dermosphenotics 
come into contact with each other medially and posteriorly as already pointed out, 
they meet the parieto-intertemporals. Anteriorly they have been covered to some extent 
by bone-plates belonging to the ethmoidal region. Their greatest width is situated 
towards the posterior end, where the dermosphenotic component is included. In this 
posterior part there issues from their ventral side in a downward and backward direction 
a powerful process which, as far as one can see, represents the alisphenoid. The 
process of each side joins either the anterior lamella of the basisphenoid (Wimania), or 
the upper surface of the proximal part of the basipterygoid process (Axelia). In the 
latter case it has also been closely joined to the cartilage that followed immediately 
dorsally of the anterior lamella. 
The fronto-dermosphenotics differ rather considerably in their extension in different 
forms. Thus while in Wimania, Coelacanthus and possibly Undina too they are longer 
than the parieto-intertemporals, in Axelia and closely related forms they are more or 
less shortened, which is also the case to a certain extent in Macropoma, where in addition 
they are strikingly small. 
A row of supraorbitals follows along the lateral margin of each fronto-dermosphenotic 
in front of the part that represents the dermosphenotic component. As far as is hitherto 
known this row of supraorbitals seems to be confined to the orbitotemporal region. The 
number of these as well as their shape seems to be subject to considerable variations. 
The smallest number observed was four (Axelia). 
The ethmoidal region is covered with a number of plates, arranged, as in Wimania > 
Axelia and other genera, according on a common basis, even though deviations in 
detail have been considerable between the different genera. It is not yet possible to 
establish whether Macropoma can also be included on the same basis with regard to 
this. If this is not the case then, however, it seems to be certain that in this fish we 
are concerned with a secondary condition. 
Anteriorly of the fronto-dermosphenotics but covering to some extent the anterior 
ends of them there follows on the ethmoidal region a paired, fairly large bone-plate, 
the postrostral (Axelia, Wimania), which in certain forms is subdivided into a posterior and 
an anterior part by a transversal suture ( Mylacanthus? or Scleracanthus? sp.). The two 
postrostrals meet on a comparatively short stretch in a median suture. Between their 
anterior ends there is a small paired or unpaired interrostral, and in front of both 
them and the interrostrals there is a transversal row of several small bone-plates, 
which have been pierced by the ethmoidal commissure of the infraorbital canal. These 
plates, called by me rostrals, may have been bounded anteriorly by the premaxillae if 
these were developed. 
The nasal capsule is covered both dorsally and laterally by the nasalo-antorbital, 
which also forms a septum between the two external nasal apertures (Axelia). 1 ) Posteriorly 
the dorsal corner of this bone is connected to the most anterior supraorbital plate, while 
z ) There is 
internal nasal aperture. 
