50 The Journal of Comparative Neurology. 



ter and the skin, and enters a foramen in the lateral aspect of 

 the dentary bone cephalad of the area of insertion of m, masse- 

 ter. Within the bone it unites with a branch of ramus men- 

 talis V, and pursues its course almost to the symphysis menti, 

 supplying branches to the lower lip, through some six or eight 

 foramina in the dentary bone. As stated in connection with 

 ramus mentalis V, it is not certain which component suppHes 

 the fibres to the skin of the lower lip. It appears to me not 

 improbable that this ramus alveolaris VII may correspond to the 

 ranms mandibularis internus VII described by Strong in the tad- 

 pole, and may therefore represent the chorda tympani. The 

 dentary being a dermal bone, the nerve may have secondarily 

 become covered by it. I have not been able to find all the 

 branches described by von Plessen and Rabinovicz and by Her- 

 rick in Salamandra and Amblystoma respectively. The ramus 

 in question must be represented by the alveolaris, accessory 

 hyo-mandibularis or buccalis of Salamandra and Amblystoma, 

 in the sense in which Herrick and v. Plessen and Rabinovicz use 

 these names. Herrick thinks, perhaps with good reason, that 

 the hyo-mandibular ramus of Amblystoma is the homologue of 

 Strong's chorda tympani or ramus mandibularis internus. If 

 my supposition regarding the homologies is correct, the latter 

 name is preferable to ramus alveolaris. Fischer's ramus mentalis 

 is really the lateral line ramus to the lower jaw and therefore 

 the branch which Strong designates as ramus mandibidaris ex- 

 termis in the tadpole. In Cryptobranchus this branch does not 

 accompany the hyo-mandibular as in the frog, but is a separate 

 ramus as far back as the ganglion. It courses laterad along the 

 dorsal face of the squamosal bone, passes ventrad of the man- 

 dible and cephalad along the ventral surface of the mylohyoid 

 muscles close to the mandible, dividing into two branches which 

 supply the gular and oral lines of lateral Une sense-organs. 



The fourth branch mentioned by Fischer as ramus jiigiilaris, 

 is the ramus hyo-majidibularis of later writers. As in other 

 amphibians it receives the ramus communicans IX ad VII. 

 The ramus hyo-mandibularis in Cyptobranchus does not contain 

 all the elements demonstrated by Strong in the nerve of that 



