MUSTELUS L.EVIS. . 185 



three bi-anclies of Mustelus accordingly represent tlie ramus 

 pretrematicus facialis sensu s trie to of Herrick and Green. 



Haller says (28, p. 414-16) tliat, in Scyllium, the nervus 

 facialis is represented by two principal branches and a third 

 smaller one. The two principal branches are said to be a 

 ramus facialis and a ramus hyoideus, the third one being said 

 to be, perhaps, a ramus palatinus. All three of the nerves 

 are said to arise independently from the so-called facial 

 ganglion, and a separate, independent, and more disial 

 ganglion is said to be found on the ramus facialis. The 

 ramus facialis becomes juxtaposited to the truncus maxillaris 

 trigemini, and this juxtaposition is said to represent an early 

 stage in that ultimate fusion of the two nerves that is said by 

 this author to be found in ganoids, and still more complete 

 in teleosts. Eeference is here made to Goronowitsch^s (25) 

 work on Lota, and it is evident, from this reference, that 

 Haller considers his ramus facialis, either in whole or in part, 

 as the homologue of Goronowitsch^s posterior division of the 

 palatinus facialis. Haller does not say whether his so-called 

 ramus facialis is, in Scyllium, a prespiracular or a post- 

 spiracular nerve, but his reference to Gegenbaur's work on 

 Hexanchus (to which I am unable to refer), and Gorono- 

 witsch's reference to the same work (24, p. 485), leaves little 

 doubt that it is prespiracular. This pretrematic part of the 

 facialis nerve of Scyllium must then have a quite different 

 course, and quite different relations to the trigeminus, to those 

 found in Mustelus. It would seem as if it must contain the 

 nerve identified by Green as the chorda tympani in the 

 selachians examined by him, that nerve, and its homologue 

 in Mustelus, accordingly being* quite certainly represented, 

 in Amia, in the maxillaris internus trigemini of my descrip- 

 tions (3). 



In Chimera Cole (11) comes to the conclusion that the so- 

 called ramus pretrematicus facialis of his descriptions is the 

 chorda tympani of the fish, and Herrick (32, p. 165) accepts this 

 conclusion as probably correct. Herrick also accepts (p. 167) as 

 probably correct my conclusion (3, p. 749) that the chorda is 



