138 EDWARD PHELPS ALLIS, JR. 



this pretrematicus internus branch of the first three vagus 

 nerves, and he says in a foot-note that it is described, but not 

 specifically named, by Bender ('06) in several of the Selachii 

 and Batoidei, and in Polypterus and Ceratodus. That branch 

 of the ramus posttrematicus of each branchial arch that is said 

 by Stannius to be distributed to the dermal tissues on the an- 

 terior surface of the arch to which it is related is not described 

 by Sewertzoff, nor shown in his figure. In Amia, I (Alhs, '97) 

 found it running downward along the anterior surface of the 

 epibranchial of the arch to which it belongs, and reaching and 

 being distributed to the internal surface of the ventral half of 

 that arch. It will accordingly be hereafter referred to as the 

 ramus posttrematicus internus. 



In work that I have under way on Polypterus, the glosso- 

 pharyngeus and first two vagus nerves each has the four so- 

 called typical branches of Sewertzoff's descriptions, and also 

 the ramus posttrematicus internus; and their homologues, in 

 somewhat modified condition, are found on the facialis and third 

 vagus nerves, and apparently also on the trigeminus. A ramus 

 dorsahs is also apparently found on both the facialis and tri- 

 geminus, as well as on the glossopharyngeus and vagus, and in 

 addition to these six branches I find, in each branchial arch, 

 a nerve running downward in its arch anterior and parallel to 

 the ramus posttrematicus. This nerve is apparently a branch 

 of the ramus anterior, and not of the ramus posttrematicus, and 

 for reasons to be later given may be called the ramus post- 

 trematicus anticus. 



Having found, in Polypterus, these several branches on each 

 of the branchial nerves, and also finding them shown, in Amia 

 (Allis, '97), on the first vagus nerve, it seemed as if they might 

 all be typical branches. I accordingly had them traced in two 

 series of transverse sections of Polyodon, both specimens approx- 

 imately 140 mm. in length, and also in a single adult, this work 

 all being done by my assistant, Mr. John Henry. 



In the two small specimens of Polyodon, the roots of the nervi 

 vagus and lineae lateralis issue together through the vagus 

 foramen, and there are no intracranial ganglion cells on either 



