1252 DR. ERIK A. STENSIO : NOTES 



The exact position of the pro- otic of Bryant's description in 

 relation to the sphenoid is not clear, but it seems to me very 

 probable that its anterior end in the fresh specimens ought to 

 have been situated much more ventraliy than it has been drawn 

 in his text-fig. 5, and at the same time also closer to the sphenoid 

 than in this text-fig. The bone actually seems to me to corre- 

 spond only to the basal parts of the corpus of the prootico- 

 opisthotic in post-Devonian Ccelacanthids (c/. Stensio, 1921, pp. 55, 

 120-121 ; 1922 a, pp. 199-201). 



The " small quadrangular bone,'" which according to Bryant i.s 

 attached by suture to the outer a.nd hinder margins of the pro-otic 

 and which extends nearly vertically upward to the cranial roof 

 (Bryant, 1919, p. 18), must evidently correspond to some dorsal 

 part of the corpus of the prootico-opisthotic in the post-Devonian 

 Ccelacanthids. The description and the figures given by Bryant 

 have failed to convince me that the bone is independent, and 

 I cannot help suspecting that in reality it may be simply a 

 broken dorsal part of the pro-otic. 



The bone which Bryant interprets as the opisthotic, much 

 resembles, as he points out (p. 18), the opisthotic in certain 

 Stegocephalians, and undoubtedly represents an opisthotic to 

 some extent. 



The two remaining bones of the region, which are both 

 small, are imperfectly known, a,nd it is not possible to decide 

 whether they are broken parts of the other bones or not. 



In the anterior half of the bottom of the labyrinth region there 

 is in the present state of preservation a large oi)ening bounded by 

 the basioccipital behind, by the sphenoid anteriorly, and by the 

 pro-otics laterally. This opening, which occurs also in Ccela- 

 canthids (Stensio, 1921, pp. 58, 121 ; 1922 a, pp. 173, 202), appa- 

 rently must ha,ve existed in Dictyonosteus too. It is situated 

 entirely behind the hypophysis, was probably traversed by the 

 anterior end of the chorda, and corresponds fairly well in its 

 position to the fenestra basicranialis posterior in the embryos of 

 reptiles (Gaupp, 1905, pp. 663, 757-760, figs. 382, 383; Allis, 

 1919 c; Stensio, 1922 a, p. 202). In the fresh specimens it was 

 probably at least to a great extent filled by cai-tilage. 



That it cannot be the fossa hypophyseos, as Bryant pre- 

 sumably means (pp. 18-19), is fully evident from tiie conditions 

 in Diciyonosteus and the Coslacanthids. 



The orbitotemporal region and the antero- ventral end of 

 the labyrinth region are occupied by a large unpaired bone, 

 the sphenoid, v^hich is on the whole very similar to that in 

 Dictyonosteus {of. pp. 2-9 above). Thus its general shape is 

 as in the latter fish, and it has a paired basipterygoid 

 process and a paired alisphenoid wulst situated in the same 

 way as in this fish [cf. Bryant, 1919, text-fig. 5 and pi. ix. figs. 

 2, 3), and the division of the cranial cavity enclosed in it as 

 well as several of the canals piercing it are in the main as in 

 this. On the other hand, if Bryant's account is correct, it 



