SUMMARY OF THE VAGUS GROUP. I 25 



2. — The pre-trematic ramus. Always very slender and 

 absent in the case of the IX nerve. Probably wholly 

 sensory. 



3. — The post-trematic ramus. Divides before entering 

 its gill into two ramuli, the dorsal purely sensory, the 

 ventral mixed. The last post-trematic ramus, however, 

 is single and sensory. 



The internal and external pharyngo-clavicularis muscles 

 are unquestionably innervated from the vagus and not from 

 the first spinals as described for selachians and siluroids. 



There are three rami cutanei dorsales of the vagus and 

 these are all distinct from the r. supra-temporalis of the 

 lateral line nerve, and from the associated communis 

 fibres (vagal root of r. lat. ace). They supply the skin of 

 the dorsal part of the operculum and the parts adjacent. 

 The most anterior (cephalic) of these rami is the ramus 

 opercularis vagi and it anastomoses with the r. opercularis 

 superficialis facialis. 



A true trapezius muscle is present in Menidia, being 

 innervated from the vagus and not from the first spinal, 

 as other authors have described for other species of 

 teleosts. Its nerve may be homologized with the n. 

 accessorius Willisii. 



The ramus lateralis vagi receives lateralis fibres from 

 the tuberculum acusticum and communis fibres from the 

 IX root. The latter correspond to the vagal root of the r. 

 lateralis accessorius of some other fishes. Its first branch, 

 the r. supra-temporalis, receives both components. 

 It distributes its lateralis fibres to two canal organs, 

 the one in the supra-temporal commissure and the other 

 in the main canal between that commissure and the 

 opercular canal. Part of the fibres supply one or two 

 naked sense organs which lie just dorsally of the main 



