532 H. H. SWINNERTON. 



The pre-etlimoid bone is abseut iu Gasterosteus. 

 The fact that it is present iu Belone (fig. 50, e. pr. b.), on 

 either side of the mesethmoid, suggests that it may be more 

 generally present than is supposed. 



The parietals (fig. 18, par.) overlap the supra-occipital, the 

 epiotic, the pterotic, and the sphenotic, and are widely 

 separated from one another. Owing to the presence of 

 cartilage beneath it and between these bones (fig. 20) it is 

 completely shut out from taking any part in the roofing of 

 the cranium. 



The frontals (fig. 18, fr.) roof over the anterior and lateral 

 cranial fontanelles (cp. figs. 4, 5, 18), Immediately in front 

 of the sphenotic each sends down a process which meets an 

 ascending process from the parasphenoid. These two over- 

 lap in such a way that the latter predominates externally. 

 A similar relation has been noticed by Klein (84, p. 145) in 

 Uranoscopus and Lophius. 



The anterior end of each nasal (figs. 10, 19, na/) sends 

 down a process which forms the anterior boundaiy of the 

 nasal aperture, lies directly on the ethmoid cartilage 

 (fig. 31, na.'), and wraps round on to the ventral surface of 

 this behind the pre-etlimoid cornu (fig. 22, oia.'), and thus 

 gives the appearance, when viewed ventrally, ot" being an 

 anterior ossification of the ethmoid. 



The two lateral wing-like processes of the parasphenoid 

 (fig. 21), by reason of their position in front of the exit of 

 the fifth nerve, cannot be regarded as the homologues of the 

 similar processes in Amia. Between them this bone is 

 pierced by two foramina for the carotid arteries. 



The only representative of the sphenoidal region seen 

 during development is the anterior plate-like extension of 

 the auditory capsule, which passes above into the post- 

 orbital process, and below into the bridge between the exits 

 of the trigeminal and facial nerves. The upper part of this 

 ossifies to form the sphenotic (o. sp.) ; the lower, the pro-otic 

 (o. pr.) ; whilst the post-orbital process, which in other 

 Teleosts forms part of the alisphenoid, remains unossified. 



