1266 DR. ERIK A. STENSIO ; NOTES 



situated (fossa trigemiDo-pituitaria, Allis, 1914 a). The basi- 

 pterygoid process is Dictyonosteus thus comprises not only the 

 homologue to the actual basipterygoid process, but also certain 

 othei' parts of the cranial wall." 



" Dorsally of the upper end of the basipterygoid process — if we 

 may, for the sake of brevity, retain the term basipterygoid process 

 for it — Dictyonosteus lacks every equivalent to the outer wall of 

 the trigemino-facialis chamber in Birgeria, Amia, Lepidosteus, 

 and Teleosts, and also to the postorbital process and the sphenotic. 

 As also no processus ascendens parasphenoidei that might have 

 covered this part of the cranial wall is present, the trigemino- 

 facialis cha.mber is consequently absolutely lacking. If a niyo- 

 dome wei'e developed in Dictyonosteus this myodome would 

 naturally be without lateral prespinal parts." 



" In Eusthenopteron (Bryant, 1919, text-fig. 5 ; pi. ix. fig. 3) a 

 basipterygoid process is found of essentially the same type as the 

 one just described in Dictyonosteus. It only reached somewhat 

 higher" up than in the latter form. In a fossa between it and 

 the vertical interorbital wall is situated the opening of the 

 canalis transversus in the same way as in Dictyonosteus. By 

 its greater extension upwards the basipterygoid process in 

 Eusthenopteron shows a certain tendency to develop in the same 

 direction as in the Ca?lacanthids. For, if we imagine its ventral 

 part reduced or weakly developed, the remaining dorsal part 

 would evidently come to correspond fairly closely to the basi- 

 pterygoid process in the Cffilacanthids, as I have already pointed 

 out in another work (Stensio, 1922 a, pp. 205-206). This iiieans 

 of course that the basipterygoid process of the Coelacanthids 

 would be homologous with at least a, part of the septum that 

 separates the myodome from either trigemino-facialis chamber in 

 Teleosts." 



" This view of the basipterygoid process in the Coelacanthids 

 is also supported by the course of the nerves and the vessels. In 

 Diplocercides hayseri, where the conditions are best known, we 

 thus find the following conditions (Stensio, 1922 a). All the 

 trigeminus branches except the r. ophthalmicus profundus must 

 have passed forward dorsally of the basipterygoid process, as has 

 the vena jugularis on its way backward after having received 

 the V. pituitaria, which tiuversed the anterior part of the 

 myodome from side to side. The r. palatinus facialis must in 

 all pi'obability on its way forwards and downwards have run 

 just postero-ventrally of the so-called basipterygoid process, and 

 probably reached down to the level of the cranial base just at 

 the myodome. The arteria carotis interna must have had its 

 course far ventrally of the so-called basipterygoid process, and 

 has, as we have seen, entered the primordial neurocranium at 

 the anterior- end of the myodome, where it turned directly 

 upwards in an unpaired canal Avhich opened into the cranial 

 cavity immediately behind the exits of the optic nerves. With 

 regard to the n. abducens, it is true that as yet nothing certain 



