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The maxillo-mandibularis branch of the external carotid runs 

 downward and backward following the mandibular branch of the 

 trigeminus, and is approximately the equivalent of the facialis and 

 mandibular branches, combined, of Allen's descriptions of the Loricati. 

 It soon sends two branches forward and downward to the muscles 

 and tissues of the cheek, and then, having reached the hind end of 

 the mandible, turns forward, with the trigeminus nerves, and there 

 separates into three parts. One of these parts runs forward along 

 the external surface of the pterygo-quadrate cartilage, between the 

 pterygoid and orbitar processes of Bridge's descriptions, the other 

 two running forward in the mandible, one internal, and the other 

 external to Meckel's cartilage. At the point where the artery turns 

 forward to separate into these three branches a short branch is sent 

 backward to the inner surface of the angle of the jaw, and there 

 breaks up immediately internal to the lining membrane of the region. 

 The lining membrane of the mouth cavity is here thickened, much 

 as it is along the dorsal ends of the gill clefts, and one or two 

 branches of the mandibularis nerve, and certain lymphatic vessels, 

 also here break up in the connective tissue immediately internal to 

 the membrane, a dense nervo-vascular tissue being formed that suggests 

 a remnant of glandular tissue of some sort, possibly the remnant of 

 a portion of the mandibular gill. 



The hyo-opercularis branch of the external carotid issues from 

 the posterior opening of the facialis canal, as already stated, and is 

 shown in one of Allen's drawings running down a certain distance 

 along the dorso-posterior edge of the hyomandibular. In other drawings, 

 of other specimens, this artery is not shown, this suggesting that it 

 may be a less important artery in the adult than it is in larvae. In 

 my larvae it first sends a large branch backward along the external 

 surface of a muscle that seems to be a levator hyomandibularis and 

 opercularis, rather than a retractor hyomandibularis, and then sends 

 a large opercular branch downward and backward in the operculum. 

 The artery then sends a branch forward across the external surface 

 of the hyomandibular to the protractor hyomandibularis muscle, and 

 a second one forward and downward across the external surface of 

 the same element and then across the external surface of the sym- 

 plectic, at the distal end of which latter element it traverses a notch 

 in the edge of the cartilage and reaches and runs forward along the 

 internal surface of Meckel's cartilage. The artery itself then continues 

 onward along the dorso-posterior edge and along the external surface 

 of the hyomandibular to the distal end of that element, where it turns 

 downward and enters the dorsal end of the hyoid arch. There it 



