354 H. W. NORRIS AND SALLY P. HUGHES 



ogies of these rami of the facialis. Regarding the ramus palati- 

 nus in a narrow sense, there can be little question. The so-called 

 chorda tympani is plainly prespiracular or pretrematic and does 

 not correspond to the chorda tympani of higher forms. 



The ramus alveolaris or mandibularis interims of amphibians 

 is variously interpreted as pretrematic or posttrematic. Druner 

 ('01, '04), who has exhaustively studied this subject, regards the 

 ramus alveolaris of the urodele amphibians as pretrematic , In 

 that case the posttrematic VII in amphibians lacks a visceral 

 sensory element. In Siren (Wilder, '91; Norris, '13) the palatine 

 and alveolar rami arise from the ganglion by a common trunk, 

 as do the palatine and pretrematic rami in Squalus. In most 

 amphibians the ramus alveolaris leaves the geniculate ganglion 

 in the hyomandibular trunk, in some separately as an indepen- 

 dent nerve. In its distribution the ramus mandibularis internus 

 of Squalus resembles more closely the ramus alveolaris of am- 

 phibians, i.e., it runs along the mesial border of the lower jaw 

 (or even within the dentary bone in amphibians), while the ramus 

 pretrematicus of sharks runs along the lateral border. In con- 

 sidering the homology of any nerve its peripheral distribution as 

 well as its origin should be taken into consideration, as Strong 

 ('90, '92) has so clearly pointed out. May it not be that the 

 ramus alveolaris of amphibians is a combined nerve, i.e., a 

 fusion of pretrematic and posttrematic visceral sensory elements? 

 Herrick ('99), indeed, suggests "that the amphibian ramus 

 mandibularis internus VII may represent both pre- and post- 

 spiracular communis elements." 



The facial nerve proper in Squalus, and presumably in all 

 sharks, is completely free from anastomoses with other nerves. 

 Jacobson's commissure, ramus communicans X ad VII, anasto- 

 moses with the ramus ophthalmicus profundus V or other parts 

 of the trigeminal nerve, are wholly absent. General cutaneous 

 elements are absent both in root and branches. It is a typical 

 facial nerve, containing only visceral sensory and visceral motor 

 components. 



The double condition of the ramus mandibularis externus VII 

 is possibly to be regarded as foreshadowing the condition in the 



