TRIASSIC FISHES FROM SPITZBERGEN 
259 
3tuhp.it oa * " a 
Text fig. 80. 
Perleidus woodwardi 
The membrane bones of the 
cranial roof, after P-177. */,. 
Ant, antorbital; Ext, extrascapu¬ 
lar; Fr, frontal; Na.ptr, nasalo- 
postrostral + interrostrals + one 
or a couple of medial rostral 
elements ;Pa, parietal; R, rostral, 
.1 aper- 
temporal; 
each lateral margin forms together with the medial margin of the antorbital (Ant) the 
boundary for the two nasal apertures of each side. As we thus see from its extension 
and relation to the sensory canals and the nasal apertures this bone-plate probably 
includes not only the homologues of the postrostrals, nasals E h p r A 
and interrostrals of the primitive Rhipidistids, but also one or 
more of the homologues of the medial rostral elements (cf.pp. 124, 
1 33 -—134, 242 above) of these fishes. 
On both sides of this so composed nasalo-postrostral, as 
for the sake of brevity I shall call the bone just described, 
there is, as in the Palaeoniscids, a large antorbital (Ant, text 
fig. 80, 81; PL 34, figs. 1, 2), which comes into contact with the 
most anterior element of the supraorbital series, with a rostral 
(R) and the most anterior element among the infraorbitajs. It 
has helped to some extent to form the anterior boundary of 
the entrance to the orbit and has, in addition, as has been 
mentioned, taken part in the boundary of the nasal apertures. 
Laterally of the nasal apertures it is penetrated longitudinally by 
a sensory canal in the same way as in the Palaeoniscids (cf. my 
account of the Palaeoniscids p. 246, and Allis, 
1889, pp. 471, 475; Pis. XLI, XLII; 1898, 
pp. 436—438; igooa, p. 438; 1905, p.491; 
Traquair, 1877 a, p. 16, PI. 1, figs. 2, 3 , 7, 
8, 11; 1879, PL 4, fig. 9; Pl. 5, fig. 1; Pl. 6, 
figs. 5, 6, 12; Stolley, 1920, the so-called 
«Antefrontale», pp. 3 i, 36 , 48, 84). 
In front of the anteriorbital on each 
side there follows, as has already been men¬ 
tioned, a bone-plate ( R , text figs. 80,81; Pl. 34, 
figs. 1, 2), which is pierced by the infraorbital 
canal and obviously must be a rostral (cf. my 
account on pp. 98, io 3 , i 33 —134, 242 above). 
This plate does not meet that of the opposite 
side, but is separated from this by the anterior 
part of the nasalo-postrostral, a part which 
for reasons given above, ought to be homo¬ 
logous with one or a couple of medial rostral 
elements. 
The orbital entrance (orb, text fig. 81; 
Pl. 33 ; Pl. 34, figs. 1, 2; Pl. 35, fig. x) is large 
and situated far forward as in Palaeoniscids 
and Platysomids. Posteriorly and ventrally 
it is bounded by a row of infraorbital bones (Ifo, text fig. 81; Pl. 33 ;P1.34, figs. 1, 2), which are, 
however, crushed and incompletely preserved, so that their number cannot be established 
with full certainty. A couple of so-called suborbitals (XA x 8 ) were also possibly present. 
Text fig. 81. Perleidus woodwardi nom. nov. 
Head from the side. Mainly after P. i85, to a smaller extent 
after P. 177 and P. 166. i/i. 
Ant, antorbital; Cl, cleithral; Dsph, dermosphenotic; Ext, extra¬ 
scapular; Fr, frontal; let, clavicle; Ifo, infraorbital plates; 
Md, mandible; Mx, maxillary; Na. ptr, nasalo-postrostral-)- 
interrostrals-f- a couple of medial rostral elements; Op, oper¬ 
culum; Pa, parietal; Pmx, premaxillary; Po, preoperculum; 
R, rostral; Rbr, branchiostegal rays ; Sc l, supracleithral; So, 
supraorbitals; Sop, suboperculum; Sscap, suprascapular; Stemp. 
it, supratemporo-intertemporal; n t , n 2 , anterior and posterior 
nasal aperture; orb, orbit; x t ,x 2 . probably so-called suborbitals. 
