34 H. B. POLLARD. 



Other details are given by Stannius. 



In Misgurmis fossilis, the mental tentacle is supplied by a R. mentalis 

 which crosses the Meckelian cartilage and then runs below that 

 cartilage. 



In Motella tricirrata the unpaired mental tentacle is supplied by a 

 R. Mentalis which takes a slightly different course. It crosses the 

 lower jaw rather far back, and then proceeds along with the R. mandi- 

 bularis of the Facial, which supplies the mandibular branch of the 

 lateral line system. This close apposition led Ziocone to the erroneous 

 view that the mental tentacle was supplied from the Hyomandibular 

 nerve of the Facial. 



The mental tentacle in Myxine is supplied by a mental branch 

 proceeding forward as in Siluroids. 



Addendum. — -I must confess to not being able to speak with any 

 feeling of certainty concerning the mental tentacle in Siluroids and 

 Cyprinoids. 



The independence of the R. mandibularis externus and the existence 

 of the separate block in Auchenaspis may be taken to represent, as an 

 alternative view to the above, a separate external tentacle or Extra- 

 mental. Gunther, in the Catalogue of Fishes mentions two pairs of 

 barbels as occurring in a number of Siluroids close to the chin. This 

 is also stated for Cobitidae, but I am in doubt whether the inner 

 smaller process is a real tentacle or only a fold of the skin. It has 

 the form of a tentacle. 



The question may be decided by examination of fuller material or 

 completer literature than has been accessible to me. 



Submandibular Tentacle. 



I have investigated the submandibular tentacle in Auchenaspis and 

 Silurus. It lies just below the coronoid process, being supported by a 

 subdermal plate of precartilage, which is very large in Auchenaspis. 

 It has no typical relation with a root piece, but from careful comparison 

 I am convinced that the Meckelian cartilage is the root piece of this 

 tentacle, precisely as in the case of the premaxillary root piece, the 

 prepalatine and the coronoid block. It is in Myxine that the Meckelian 

 cartilage, or anterolateral piece of the tongue apparatus most closely 

 resembles a root piece, a supposition strengthened by the disposition of 

 the nerves. Occurrence of the submandibular tentacle is rare in fish. 



