396 "• '*• I*<^I'I'ARD, 



According to Sa(;l:.meiil, such a nasal labial occurs in many 

 Cyprinoids and perhaps in all; and also in the Characinidae. No 

 doubt on special search it might be found in very many other groups 

 of Teleostei. 



The nasal labial of Selachii has been described in rich detail by 

 Johannes Müller and Gegenbaur. Many references to such struc- 

 tures have been made by Pahkkr, but subs(>quent investigation has 

 shown his observations to be unfortunately unreliable. 



In many Selachii the nasal labial is fused Nvitli the edge of the 

 nasal ca])sule. and indeed Gegenbaur concludes that it is a portion 

 cut otî" from the cranium. That however is controverted by compa- 

 rison outside the Selachii. In the Dipnoi there is a trelliswork of 

 cartilage forming the wall of the olfactory capsule and, in view of the 

 frequent fusion of the nasal labial with the cranium in Selachii, this 

 trelliswork may perhaps be held to represent a nasal labial. 



The nasal capsule and tube of Myxine is surrounded by irregular 

 rings of procartilage, which represent the nasal labials. Gegenbaur, 

 in mentioning this view, concludes that it is a hasty one, but all 

 doubt seems to be removed by the fact that the nasal tube is worked 

 by a muscle, the Nasalis of Fi^rbringer or "Zuriickzieher der Nasen- 

 öÖ'nung" of Müller, which belongs to the tentacular system and is 

 supplied by the Ophthalmicus profundus, while the nasal tube itself 

 receives sensory branches from the Ophthalmicus profundus. The 

 compressor narium M., ethmoideouasalis F., and a portion of the 

 transversus oris F. are also attached to the nasal tube. 



On this point Müller remarks that "Since two olfactory nerves 

 proceed into the single olfactory capsule, the single olfactory capsule 

 is to be explained rather by the apposition than fusion of the nasal 

 capsules of cartilaginous fish, and this hajjpens indisputably through 

 the suppression of those i)arts which otherwise lie between the nasal 

 capsules". While agreeing with Müller in principle, I regard the 

 supporting elements of the nasal capsule of Myxine as corresponding 

 only to the nasal labial of Selachii, not to the whole capsule. 



Furthermore no one, who has examined a series of sections of 

 the head of Myxine^ can doubt that the plate supjjorting the posterior 

 part of the nasal or hypophysial tube where it opens into the i)alate, 

 the "Gaumenplatte" of Müller or "posterior iutertrabecula" of 

 Parker is a posterior continuation of the nasal skeleton, and as such 

 ultimately to be derived from a nasal tentacle. 



Müller compared the nasal cartilages of Chimaera with the 



