573 



In Cottus this outer wall is entirely of membrane, the inner wall of 

 the chamber thus here forming the outer surface of the prepared skull, 

 and the trigeminus ganglion having an apparently extracranial position. 

 The internal wall of the chamber forms, in all the fishes examined, 

 part of the bounding walls of a recess on the internal surface of the 

 skull, and this recess lodges the lateralis and communis portions of 

 the V— VII ganglionic complex. In Amia these portions of the gan- 

 glionic complex lie in the upper lateral chamber of the myodome. 

 There is accordingly question as to whether the inner wall of the 

 chamber of teleosts corresponds exactly to the same wall in Amia. In 

 any event, the recess that lodges, in teleosts, the lateralis and com- 

 munis ganglia would seem to be the homologue of some part of the 

 aqueduct of Fallopius. 



The trigemino-facialis chamber is continued anteriorly by an in- 

 tramural space that lodges the jugular vein and truncus ciliaris pro- 

 fundi. The outer wall of this space is largely of membrane in all the 

 mail-cheeked fishes examined, excepting Cottus and there appears as a 

 jugular groove on the outer surface of the prepared skull. In Cottus 

 the outer wall of the space is of bone and the inner wall largely of 

 membrane, the space thus appearing, in this fish, as a recess on the 

 inner surface of the prepared skull. The outer wall of the space, 

 primarily of membrane, is invaded to a difierent extent, in different 

 fishes, by the neighbouring bones, thus giving rise to greatly varying 

 conditions. 



14. In all the Loricati examined, the ramus palatinus facialis 

 either perforates the proötic bridge or adjoining portions of the side 

 wall of the proötic and so passes from the cranial cavity directly into 

 the myodome. In all of the Craniomi examined, this nerve first passes 

 from the cranial cavity into the trigemino-facialis chamber and then 

 traverses that chamber to issue by its trigeminuSfOpening and so enter 

 the myodome. 



15. Dactylopterus differs markedly, in many respects, from the 

 other mail-cheeked fishes examined; notably, in the absence of a 

 mesethmoid bone; in the fusion of the nasals to form the single so- 

 called median ethmoid of current descriptions; in the compression of 

 the posterior portion of the skull, this producing great changes in all 

 the bones of the region ; in the absence of a temporal fossa ; in the 

 apparent absence of a ramus mandibularis internus faciahs; in the 

 course of the nervus abducens; and in certain features of the latero- 

 sensory canals. 



Palais de Carnoles, Mentone, March 28th, 1907. 



