4 2 
ERIK A : SON STENSIO 
The most striking resemblance between the Coelacanthids and the Temnospondylous 
and Stereospondylous Stegocephalians with regard to the ossifications of the primordial 
neurocranium is seen in the orbito-temporal region. If we first examine the basisphenoid 
we find that in such forms as Loxomma , Eryops, Laccocephalus, Capitosaurus 1 ) etc. (Huene, 
1913, pp. 3ig—322, fig. 6 ; Broom, igi3e, p. 587, fig. 14; Broili, 1917, pp. 572—574; 1918, 
p. 173; Watson, 1912a, pp. 2 — 3, 7—9; 1916, pp. 6x2—618, 63i — 632; 1919, pp. 10, ig, 27, 
51—59, figs, xi, 12) it showed the same conditions as in the Coelacanthids. Thus it 
is situated with its corpus behind the fossa hypophyseos and as the corpus is often 
rather high it forms a high dorsum sellae. To judge from this position it seems probable 
that the corpus belongs to the chordal position of the cranium. Basipterygoid pro¬ 
cesses are often developed in primitive forms such as Loxomma, Pteroplax, Eryops, 
Actinodon, Archegosaurus, Cacops, Broiliellus, etc., but are generally lacking in younger 
and more specialized forms. — Watson (1912 a, pp. 9—10) has shown in Megalichthys 
that with regard to the basisphenoid the Rhipidistids are developed in about the same 
way as the Coelacanthids and thus present a good resemblance to the Stegocephalians. 
I have myself pointed out above (p. 60) that this was also true in Dictyonosteus, although 
in this species the basisphenoid is not, however, an independent bone but forms a part 
of the large sphenoid. 
The ossified part of the interorbital wall which constitutes the alisphenoid in the 
Coelacanthids is part of the so-called sphenethmoid in Eryops (Broom, 19i 3 e, pp. 587 
588, figs. 14 — 17; Watson, 1919, fig. 11 A,B; Broili, 1917, pp. 572—574), Pteroplax (Watson 
1912 a, p. 7), Lyrocephalus (Wiman, 1916 b, pp. 216 — 219, PI. XVI, fig. 4) and probably 
other allied forms (cf. Broili, 1918, p. 173) in exactly the same way as the pars ali- 
sphenoidea in Dictyonosteus is part of the sphenoid. It seems also probable that in certain 
primitive Stegocephalians the basisphenoid too was an integral part of the so-called 
sphenethmoid (Pteroplax, Watson 1912 a, p. 7; 1917 p. 981), and, if this be true, we 
consequently have also in this respect a remarkable agreement between them and 
Dictyonosteus. Finally it is also worthy of mention that both in primitive Stegocephalians 
and in Dictyonosteus the middle and anterior parts of the so-called sphenethmoid and 
sphenoid respectively seem to correspond most closely to the orbitosphenoid. 
With regard to the skeleton of the ethmoidal region it is of interest in this 
connection to find how in such forms among the Stegocephalians as Eryops, Trimero- 
rhachis. and Zatrachys the septomaxillaries seem to occupy almost the same position in 
relation to the nasal capsules as the preethmoids in the Coelacanthids (cf. Broom, 
igi3 e, figs. 11, 19, 21; Abel, 1919, p. 237, figs. 185, 202, 211). According to the 
prevalent view, however, the septomaxillaries are supposed to belong to the category 
of membrane bones, while the preethmoid, as we have seen, forms an ossification in the 
ventral and middle part of the cartilage of the ethmoidal region. Gaupp (1905, pp. 617, 
746, 756, 773) also states very definitely with regard to the recent Amphibia and Reptilia 
that the septomaxillaries are not to be homologized with the preethmoids. 
Huene’s (igi3 ), Broom’s (igi3e) and Watson’s (1916; 1919) descriptions and figures 
of Eryops and Capitosaurus (£f. also Broili, 1917; Abel, 1919) show very clearly 
[ ) According to Watson (1919, p. 27) the basisphenoid is paired in Capitosaurus. 
