178 EDWAKD PHELPS ALLJS, JUN. 



muscley, and continues backward to join, or form ])ai't of, 

 the aponeurosis that separates tlie superior and niandibuhir 

 parts of the adductor. A second part has its insertion on the 

 anterior end of the posterior upper labial cartilage. The 

 third part continues backward parallel to, and slightly tlorso- 

 mcsial to, the latter cartilage, and has its insertion on the 

 dorso-posterior end of the mandibular labial cartilage. 1'his 

 insertion of these tendons of Add/3 on these two labial car- 

 tilages certainly indicates that a })art, at least, of the muscle 

 Ijelongs to a pre-oral arch, if the labial cartilages do, as I 

 believe is very generally accepted. The nerve that innervates 

 these parts of Add/3 must then belong to the same arch, and 

 must be a motor component of the post-trematic nerve of the 

 arch. Hottmann, it should be noted, says (34, p. 266) that the 

 muscle Add/3 arises from the u})per part of the wall of the 

 " Kieferbogenhohle," an origin which would seem to preclude 

 its belonging to a pre-oral arch. 



After giving off this motor branch to the muscle Add/3 

 the ramus mandibuhiris sends a relatively snudl but still im- 

 portant branch downward and backward along the external 

 surface of the adductor. When it reaches, approximately, 

 the level of the anterior end of the posterior upper labial car- 

 tilage it turns forward a short distance, then mesially, and 

 then downward, laterally, and backward into the maxillary 

 labial fold, there lying dorsal to the labial cartilage. If the 

 cartilage belongs to a pre-oral arch, this branch of the man- 

 dibuhiris thus has the relations to the mouth, considered as a 

 cleft, of a ramus pre-trematicus, the ramus mandibuhiris itself 

 being the related ramus post-trematicus. Considering it as 

 such a branch it would be the ramus braiichialis posterior of the 

 })osterior labial arch, the motor nerve to the muscle Add/3 being 

 the motor component of the ramus braiichialis anterior of the 

 same arch. Those two branches of the ramus inaxillaris 

 superior trigemini that are also distributed to the labial fold 

 of the fish Avould then either be the sensory components of 

 the rinuus l)ranchialis antci'ior of the same arch, or perluips 

 be, respectively, the pre- and post-trematic branches of the 



