ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 717 



A fairly powerful flat muscle, which arises from the ventral or convex margin of the 

 cornual cartilage at the bend immediately in front of the origin of the hyo-copulo- 

 palatinus, and opposite the insertion of the palato-ethmoidalis profundus. It is covered 

 externally partly by the first two myotomes behind and partly by the superficial and 

 deep copulo-glossus muscles below. In the sections the cornual cartilage appears in 

 about 140 sections, of which 60 are in front of the origin of the copulo-palatinus and 

 20 behind it. 



The fibres of the copulo-palatinus course downwards and backwards, somewhat 

 diverging, bend over the external bar of the anterior segment of the basal plate external 

 to the first head of the copulo-tentaculo-coronarius on to the internal bar of the same, 

 into the sheath of the ventral surface of which it is inserted near the middle line from 

 its extreme anterior margin up to the commencement of the median fenestra. In the 

 sections it is continued slightly behind and at the side of the fenestra, and, further, it 

 is seen that the two muscles are joined up below the internal bar by a median ligament, 

 and that the latter is attached, and not very securely, at about the middle line of the 

 internal bar. 



In front of the anterior margin of the internal bar of the basal plate the external 

 fascia of the copulo-palatinus is observed in the sections to fuse with the longitudinal 

 sheet of fascia stated by J. Muller and P. Furbringer to be the tendon of the hyo- 

 copulo-glossus (q.v.). It presents the appearance in the sections as if some of the fibres 

 of the present muscle were inserted into this sheet also. 



As pointed out by P. Furbringer, the function of this muscle will depend upon 

 which end of it acts as the fixed point. As far as the copulo-palatinus is concerned the 

 cornual cartilage can be fixed by the palato-ethmoidalis profundus, in which case the 

 muscle would tend to approximate the external bars of the anterior segment of the 

 basal plate, and thus compress the mouth cavity laterally, and approximate the two 

 halves of the dental apparatus dorsally. When, however, the cornual cartilage is not 

 fixed, the contraction of the copulo-palatinus would of course depress it. J. Muller 

 states that the muscle elevates the basal plate and draws it somewhat forwards, in that 

 way shutting the mouth. He also recognises that it may also compress the mouth 

 cavity laterally. 



22. M. hyo-copulo-poMtinus. (Fig. 3, h. c. p.) 



J. Muller, [Erster] Vorwartszieher des Zungenbeins (p. 248). Vorderer Vorzieher des 

 Zungenbeins (p. 322). Erster Vorzieher des Zungenbeins (p. 324). 



A wide, powerful muscle, covered externally by about the first three myotomes, and 

 its dorsal border situated immediately below the ventral border of the tentacularis 

 posterior in front. 



The hyo-copulo-palatinus arose, in a dissection, mostly from the external fascia of the 

 copulo-quadratus profundus at about the middle and upper portions of its course. A 

 few fibres, however, arose in front from about the middle of the cornual cartilage 



