The oral cirri of Siluroids and the oripin of the liead in Vertebrates. 401 



Therefore, in considering its homologies, various components must 

 be recognised in the palatine, and I consider the most anterior 

 branches a dissociated portion of the R. premaxillaris. The most 

 anterior tentacle of Cyprinoids is supplied by a nerve, of which 

 BüciiNEU has given a most excellent description (in Barbus). He 

 terms it niaxillaris superior. "It springs from the anterior internal 

 border of the ganglion, passes in a canal formed by the upper convex 

 face of the body of the sphenoid (parasphenoid) and the base of the 

 greater (prootic) and lesser wing (orbitosphenoid) and is directed 

 along the internal wall of the orbit, passes between the anterior 

 frontal (ectethmoid) and palatine along the vomer and forms a kind 

 of plexus with a branch of the maxillaris inferior (R. mx. superior). 

 From this plexus start three branches for the two barbels and for 

 the fleshy lip along the intermaxillary. That of the superior barbel 

 passes through a foramen, hollowed out at the internal extremity of 

 the maxillary bone." 



Sägemehl has described the nerve as palatine in Cyprinoids and 

 agrees with Büchner, and I have myself followed the course of the 

 nerve by sections and dissections in Misgtirnus fossilis. It takes a 

 course intermediate between those of the R. premaxillaris and R. pa- 

 latinus of Siluroids, inasmuch as it passes below the prepalatine piece. 

 I take it therefore, that this nerve almost universally termed palatine 

 contiiins palatine and premaxillary fibres and corresponds to the Pre- 

 maxillaris of Myxine. 



The R. palatinus has been described in detail in the Sturgeon by 

 Stanntus and v. Wijhe. "In Acipenser the N. palatinus has relations 

 really corresponding to those of Teleostei" (Stannius). "It runs 

 forward along the lateral edge of the parasphenoid, separated from 

 the orbit by a paired outgrowth of cartilage from the Basis cranii. 

 In front of this the nerve forms a network with the Ramus maxil- 

 laris superior, and then sends branches to the snout and ends in the 

 tentacles" (v. Wijhe). 



The barbels of Sturgeons are therefore premaxillary and maxillary 

 tentacles. 



Maxillary and coroiioid Tentacles. 



Maxillary tentacles are shown most typically in Trichomycierus 

 and Callichthys (Figs. 5, 6 and 7). They are supported, through the 

 intorniediation of a small maxillary bone (os labial Cr vier, adnasal 

 Mc. MuRRicn), on the prepalatine piece and extend downwards and 



