ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 691 



with the tentaculo-ethmoidalis. P. Furbringer believes that its function is to assist 

 the suctorial action of the mouth, whilst that of the transverse commissure is to 

 approximate the second tentacles. It is, however, questionable whether the mouth of 

 Myxinoids is ever suctorial, and further, the transverse commissure extends beyond 

 the base of the second tentacles. 



6. M. nasalis. (Figs. 3, 8, 9, 11, nas.) 



J. MCller, Zuriickzieher der Nasenoffnung (p. 258). 

 ,, Zuriickzieher der dussem Nase (p. 322). 



,, Zuriickzieher der Schnautze (p. 323). 



Arises by two small fasciculi largely from the tough membrane enclosing the roof 

 (external superficial fascia), but also from that covering the side of the nasal chamber 

 at about the anterior half of the latter. It passes straight forwards, partly obscuring 

 the nasal chamber and nasal tube, and is inserted as follows : — (a) into the inter- 

 nal process of the lateral labial cartilage (cp. Part I., figs. 1 and 2, and present 

 Part, fig. 3) ; (b) into the ventral longitudinal bar connecting the anterior nasal 

 rings. This bar is also connected by ligament with the process above, in this respect 

 differing from Bdellostoma according to Ayers and Jackson, who state that 

 the process is joined by ligament to the nasal tube, but not to any cartilages of 

 the tube ; (c) into the lateral wall of the anterior extremity of the nasal tube itself, 

 in front of the third nasal ring ; (d) into a dorsal forwardly-directed process 

 from the second nasal ring. This process is not always found, and may be present 

 on one side and not on the other. It is figured by Pollard ; * (e) joins with 

 the vertical ethmoideo-nasalis (cp. fig. 3), and is inserted into the first nasal ring 

 and the side wall of the external nasal opening. This is the only insertion mentioned 

 by P. Furbringer. 



For the greater part of its length the M. nasalis is seen to consist in transverse 

 section of two large fasciculi — a dorsal triangular one and a larger ventral oval or 

 quadrangular one. The whole forms in section a large triangular mass, with its base 

 resting on the dorsal edge of the tentacularis posterior (behind) and on the outer 

 dorsal surface of the palato-ethmoidalis superficialis. 



According to J. Muller, the muscle is very differently related in Bdellostoma. 

 He states that it arises from the palatine bar, and is inserted not only into the anterior 

 end of the nasal tube, but also into the transverse labial cartilage. In Myxine it does 

 not even approach either of these cartilages. 



The function of the nasalis, when not neutralised by the ethmoideo-nasalis, would 

 be to draw the nasal opening and the lateral labial cartilage backwards and somewhat 

 upwards. 



* Zool. Jahrb., Abt. Morph., viii., fig. 11. 

 TRANS. ROY. SOC. EDIN., VOL. XLV. PART III. (NO. 26). 99 



