the Coelacanth Fish. 335 



identical position in all Osteolepids, and by itself goes far 

 to establisli a derivation of the Coelacantlis from that group. 



In a paper now ready for publication I have pointed out 

 that the long unossitied region which separates the basi- 

 sphenoid and basioccipital of Osteolepids, as shown in Bryant's 

 description of Eustheuopteron, is functionally connected with 

 the iiiiio-e in the dorsal roof of the head. 



The neural cranium of Coelacantlis is very difficult to 

 interpret. Dr. Stensio is, of course, perfectly correct in his 

 interpretation of the " sphenoid.'''' It is probable that the 

 most dorsal foramen ))assing through that bone is for the 

 opthalmicus profundus, and that the lower and most anterior 

 of these transmitted the third or sixth nerve. Tlie remaining 

 loranien may have transmitted the trociilearius. 



I am very doubtful of Stensio's interpretation of the space 

 between the basisphenoid and parasphenoid as a myodome. 

 In Macropoma the basisphenoid fades away gradually until 

 it is repiesented only by bony spicules. In different indi- 

 viduals there is some evidence that there is a progressive 

 growth of bone into this region, and the conclusion seems 

 obvi >us that it was in life occupied by cartilage which failed 

 to ossify. The basisphenoids of Macropoma, Winuniia, and 

 Axelia are much less completc-ly ossified than those of the 

 Coal Measure and Upper Permian Coelacantlis. In these 

 foinis the liinder surface of the basis[)henoid is formed by a 

 large, nearly circular, concave condjle, extended laterally 

 and upward by small additional faces ; it is entirely identical 

 with that of Megdliehthys. In these forms it is most 

 ])robable that the lower surface of the basisphenoid is in 

 direct contact with the parasphenoid. 



In any case, the position of this hole is not that of the 

 Pi.laeoniscid my(id me which lies dorsal to the basi[)terygoid 

 process and lateral of the body of the basisphenoid. 



Tlie large bone called by Stensio the prootico-oj)istliotic 

 C( rr('>ponds most accurately with the prootic in Easthenu- 

 2>ieron (Bryant, 1919). The two bones agree in articulaiing 

 with the lateral borders of the basioccipital, and stretching- 

 forward in trout of that bone along the sides of the great 

 unossitied tract of the basis cranii. In Osteolepids they do 

 not leacli the basisphenoid as they do in Coelacantlis. In 

 both foiins there are anterior and posterior flanges from the 

 skull-roof which meet or nearly meet the upper edge of the 

 ])iu()iic. The two bones differ, however, in the absence in 

 En.ff/ieuopteron ot the pocket; wdiicli occupies the hinder part 

 of the side of the Coehicanth piootic. Tlie funclion of this 



