302 
ERIK A : SON STENSIO 
Plate 20. 
Fig. i. Scleracanthus asper n. sp., part of an external bone of the head from impression in the stone. 
The character of the ornament clearly shown. After specimen P. 242 c. 
» 2. My-lacanthus spinosus n. sp., operculum preserved as impression of the inner surface ( P. 7.03). 
» 3. Lyrocephalus euri Wiman, parts of the neurocranium and visceral skeleton of the right side 
(orig. of Wiman 1916). 
» 4. » » » parts of the neurocranium and visceral skeleton of the left side 
with the prootic and opisthotic in situ. 
» 5- Polypterus sp., part of neurocranium seen from the left side showing the prootic (Pro) at 
the anterior end of the bulla acustica saccularis (b. a). 
» 6. Birgeria mougeoti (Agassiz) neurocranium (P. i 65 ) seen from the right side. In the posterior 
half certain lateral parts both of the sphenoid ( Sph ) and the 
prootico-opisthotic (Pro. 0) removed. 
Explanation of index letters 
Alsph, autosphenotic (in fig. 5); Bo, basioccipital; Co. a, columella auris; Epo, epiotico-opisthotic; 
Eppt, epipterygoid; O, opisthotic, Pp, postparietal (ventral process); Pro, prootic; Pro. 0, prootico- 
opisthotic; Pspli, parasphenoid; Pt, pterygoid; Q11, quadrate; Sph, sphenoid; al, anterior portion of 
the partes laterales of the sphenoid; a. car. int , paired foramen for arteria carotis interna; a. opt. 
foramen probably for the arteria optica; b, process on the posterior margin of the pars lateralis of the 
sphenoid; b. a, bulla acustica saccularis; bsph, part of the pars basalis of the sphenoid between 
the fenestra optica and the canalis transversus; c, processus on the posterior margin of the pars 
lateralis of the sphenoid; d, portion of the pars basalis of the sphenoid anterior to the fenestra 
optica; fc, canalis facialis (posterior opening); fen. opt, fenestra optica; my, fossa in which the 
musculus rectus externus had its origin. At the anterior end of this fossa lies the opening of the 
canalis transversus. The fossa corresponds partly to the myodom of Amia and Teleosts; n. olf, canal 
for the nn. olfactorii through the sphenoid; pi, profound lamella of the parasphenoid; pr. asc, processus 
ascendens of the epipterygoid; pr. ot, processus oticus of the epipterygoid; V4, foramen probably 
for the vena cerebralis anterior; II, for opticum; III, foramen oculomotorii; IV, foramen trochlearis; 
V, place of exit for the trigeminal except r. ophthalmicus profundus. The n. buccalis lateralis was 
also transmitted at this place; V1, canal for r. ophthalmicus profundus in section; X, incisure on the 
opisthotic indicating the course of the vagus nerve through the cranial wall backwards. 
Plate 21. 
Fig. 1—3. Birgeria mougeoti (Agassiz), sphenoid after a model made in accordance with my obser¬ 
vations in specimen P. i 65 . The model is reproduced in ventral 
(fig. 1), dorsal (fig. 2) and lateral (fig. 2) aspects. 
» 4. >' » » anterior part of the caudal region (P. i 65 ) with dorsal and 
anal fins. 
» 5—7. » » - teeth P. 626, P. 628, P. 884 respectively. The teeth P. 626' 
and P, 628 with magnification °/ 2 , and tooth P. 884 with 
magnification 3 / 2 . 
Explanation of index letters. 
A, anal fin; Bd, basidorsal; Bv, basiventral (probably only distal part); Ch, chorda-space; 
D, dorsal fin; Id, interdorsal; Iv, interventral (-{- probably a proximal part of the basiventral); 
Ms, baseost; Ps, axonost; Ps+Ms, long ossifications in the majority of the endoskeletal radials 
of the anal fin, perhaps formed by the fusion of originally independent axonosts and baseosts; 
a, aj, corners on the edge between the latero-dorsal and the lateral surface of the sphenoid; a. car, 
