272 



The nerve that arises from the ventral surface of the maxillo- 

 mandibularis ganglion, is a large nerve trunk. It arises from the 

 anterior end of the ganglion, and separates at once into three branches. 

 Two of these three branches again immediately separate each into two 

 nearly equal branches, and the four nerves that so arise may even be 

 said to each have an independent origin from the ganglion, close to 

 each other and close to the remaining large single branch. These 

 several nerves, together with the motor root of the complex, form the 

 ramus maxillo-mandibularis trigemini of the fish, which runs downward 

 and laterally through fenestra 1 , almost completely filling it, so that 

 the fenestra is practically the foramen of the nerve. The several 

 branches of the nerve thus all pass dorsal to the trabecular bar, but 

 ventral to the so-called pterygo- quadrate. Huxley (13) has already 

 called attention to the singular anomaly of this relation of this nerve 

 trunk in Myxine and Petromyzon to a pterygo-quadrate cartilage, and 

 says that "in all other vertebrates" it has its course "on the dorsal 

 aspect of the palatine arcade" and not on the ventral. The probable 

 explanation of this apparent anomaly will be given in discussing the 

 skull. 



The anterior one of the three main branches of the maxillo- 

 mandibularis runs laterally and forward under, the anterior end of the 

 pterygo-quadrate, and then lies for a while ventral to the hind end 

 of the palatine. It here lies lateral to the velar muscles, between 

 them and the dorsal portion of the m. copulo-quadratus profundus. 

 Continuing forward, it soon passes outward across the ventral surface 

 of the hind end of the m. palato-coronarius and acquires a position 

 between that muscle dorso-internally and the m. copulo-quadratus pro- 

 fundus externally. When it has passed beyond the anterior edge of 

 the m. copulo-quadratus profundus it lies slightly dorsal to the dorso- 

 lateral edge of the external bar of the anterior segment of the copula, 

 and immediately internal to the adjoining edges of the m. hyo-copulo- 

 palatinus and m. copulo-palatinus. Kemaining in this position it 

 passes ventral to the lateral edge of the palatine commissure, and 

 beyond that commissure lies ventro-mesial to the cornual cartilage, 

 between the m. copulo-palatinus externally, the m. copulo-ethmoidalis 

 ventro-mesially , and the m. palato-ethmoidalis profundus dorsally 

 This latter muscle I find, however, in B. dombeyi, as two wholly 

 separate muscles, one lying dorsal to the other and the two crossing 

 each other at an angle. Both muscles extend from the nasal bar to 

 the cornual cartilage, and they both must act as adductors of that 

 cartilage, drawing it toward the nasal bar. The nerve here under 



