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ERIK A : SON STENSIO 
One may venture to put the total length of the two specimens (P. 772 and P. 174) 
at about 35 to 45 cm. The shape of the body was probably fusiform, but no details 
can be established about it. 
The primordial neurocranium and its ossifications. 
As in Birgeria mougeoti the primordial neurocranium is composed to a considerable 
extent of replacing bones, but is very much crushed and compressed from the sides, 
so that only a few details can be observed. 
In the labyrinth region are found remains of a large prootico-opisthotic (Pro. 0, 
PI. 3 i, figs. 1, 2; PI, 32 , fig. 3 ), evidently homologous to the similarly termed bone in 
Birgeria mougeoti, to which it also seems to correspond in its extension (cf. pp. 153— 
161 above). 
As in Birgeria mougeoti the wall of the neurocranium was cartilaginous immediately in 
front of the prootico-opisthotic (PI. 3 i, figs. 1, 2; PI. 32 , fig. 3 ). Anteriorly of this cartilage 
quite as in Birgeria mougeoti (cf. pp. 161—175 above), there follows the posterior part of the 
large sphenoid (Sph, PI. 3 i, figs. 1, 2; PI. 32 , fig. 3 ) which, in my description of Birgeria 
mougeoti, I have shown reaches with its basal parts into the most anterior part of the 
labyrinth region, while its main part falls within the orbitotemporal region. An incisure 
(V) on the posterior margin of the sphenoid indicating the exit of the second and third 
branches of the trigeminus can be observed, but it is somewhat more completely 
enclosed by bone than in Birgeria mougeoti. It does not even seem impossible that it 
was bounded caudally by a thin bridge of bone and that the trigeminus would thus 
pierce the sphenoid in the immediate proximity of the posterior margin. Nothing is 
preserved of the anterior parts of the sphenoid. 
Both the substitution bones described in the neurocranium have no radiation and 
consist exclusively of a cancellous bone substance as in Birgeria mougeoti (cf. pp. 152—153). 
What has been shown here is certainly not much in itself, but it is all the same 
of great importance as it supports the view that the ossifications of the primordial neu¬ 
rocranium in Palaeoniscids in general were on the whole developed as in Birgeria mougeoti. 
The membrane bones of the neurocranium. 
The parasphenoid (Pspli, PI. 3 i, figs. 1, 2; PI. 32 , fig. 3 ) was wide and presumably, 
rather strong beneath the orbitotemporal region. Under the labyrinth region it is only 
represented by fragments. Nothing else is known as to its shape and relations. 
Nothing is preserved of the membrane bones of the cranial roof in the material 
present. 
Visceral skeleton. 
The palatoquadrate seems apparently to have been triangular as in Boreosomus 
arcticus, but no further details as to its shape can be established. Of its substitution 
bones the metapterygoid (Mptg, PI. 3 i, fig. 3 ) and the quadrate (Q_u, text fig. 72, PI. 3 i, 
fig. 1) are present in a very fragmentary condition, and it is uncertain whether they were 
separate bones or fused as in Boreosomus arcticus. Of the membrane bones the ecto- and 
entopterygoid are present, except for their most anterior parts. 
