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turns out to belong here, then it would show that the species had a rather conside¬ 
rable size. 
The membrane bones of the neurocranium. 
Nothing is preserved of the substitution bones of the primordial neurocranium and 
of the membrane bones there are only certain ones belonging to the cranial roof (PI. 27, 
fig. 3), namely the frontal (Fr), dermosphenotic. parietal (Pa) supratemporo-intertemporal 
(Stemp. it) and a large extrascapular (Ext). 1 ) Nothing further can be established as to 
the shapes of and relations between these bones. Their sculpture consists of longitudinal 
striae, which are somewhat long and fairly coarse on the anterior parts of the frontals, 
becoming rather short and fine further backwards on the parietals, supratemporo-inter- 
temporals and extrascapulars, where they may be replaced by tubercles at several places. 
Visceral skeleton. 
The palatoquadrate is not preserved on the present 
material of this species. 
The maxillary (Mr, text fig. 71; PI. 28, fig. 1) is 
ncompletely preserved and partly broken, but one can 
certainly see that its shape cannot as a whole have dif¬ 
fered very essentially from the usual one in the Palae- 
oniscids. 
The mandible (Md, text fig. 71; PI. 28, fig. 1) is 
long and robust and almost the same height through¬ 
out its length, as the lower margin is straight for a 
considerable stretch and runs parallel to the upper one. 
As is usual in the Palaeoniscids it has no coronoid process. 
The preoperculum ( Po, text fig. 71; PI. 28, fig. 1) 
is an angular bone, extending forward towards the 
orbital opening in the usual way. 
The hyomandibular must have been oblique as in 
the majority of Palaeoniscids. 
The operculum (Op, text fig. 71; PI. 25, fig. x) is partly incomplete. It is obvious, 
however, that it was both large and wide, with the anterior margin concave, the 
posterior one convex and the lower one fairly straight. 
The suboperculum (Sop, text fig. 71; PI. 28, fig. 1) is very fragmentarily preserved 
and nothing can be established with certainty as to its shape or size. 
The radii branchiostegi (Rbr, text fig. 71; PI. 28, fig. 1) must have been few in 
number. Only four are present, and it is improbable that the total number exceeded 
five. They are long and rather uniformly wide. 
In front of the radii branchiostegi there follows between the two mandibulae an 
unpaired and very large median jugular plate (Mg, text fig. 71; PI. 28, fig. 1). 
Text fig. 71. 
Boreosomus reuterskioldi n. sp. 
Parts of the visceral skeleton. 
After P. ng. V,. 
Md; mandible; Mg, median jugular plate; 
Mx, maxillary; Op, operculum; Po, pre¬ 
operculum; Rbr, radii branchiostegi; Sop, 
suboperculum. 
I ) The extrascapulars must obviously be only two in number, one on either side of the median line. At least 
in certain Palaeoniscids they are, on the contrary, represented by a number of small plates (Traquair, 1877 a, p. 21; 
1901, p. 83; PI. XIV, fig. I. 
