544 H. W. NORRIS AND SALLY P. HUGHES 



trachea; 4) m. interbranchialis 4 (hyotrachealis, auct.)- This lat- 

 ter muscle is a small slip attached to the extreme posterior end 

 of the third branchial cartilage, running thence posteriorly, 

 medially and ventrally and inserted on the lateral border of the 

 trachea (fig. 40. ib.4). In Dermophis this is apparently a pos- 

 terior part of the hyopharyngeus of Goppert (dorsolaryngeus 

 (a)). 



5. General considerations on the glossopharyngeal and vagus neries 



As in other amphibia, the ninth and tenth nerves in the caecil- 

 ians are closely associated, both in roots and in ganglia. It is 

 possible, however, in some instances to distinguish sharply be- 

 tween them. It is then seen that the ninth nerve has the char- 

 acteristic composition of visceral sensory and visceral motor 

 fibers. A ramus pretrematicus IX, a very conspicuous nerve 

 in the Urodela, with characteristic Jacobson's commissure con- 

 necting with the facial nerve, is absent. But if we rightly inter- 

 pret Marcus' figures, a well differentiated ramus pretrematicus 

 IX occurs in the larval stage (Hypogeophis). In the late larval 

 stage of Ichthyophis the writers find no ramus pretrematicus 

 IX. A 'ramus communicans' between the tenth (and ninth) and 

 the seventh nerves, so characteristic of other amphibians is ab- 

 sent in the caecilians. A dorsal cutaneous branch (ramus auricu- 

 laris X of Urodela and Anura) of the vagus does not exist. 

 This is somewhat remarkable, as in other Amphibia it is a con- 

 spicuous nerve in the occipital region. Wiedersheim figures a 

 dorsal branch of the vagus, but he evidently mistakes the occip- 

 ital nerve for this. The absence of limbs is correlated with a 

 lack of the trapezius and omo-arcualis muscles with their inner- 

 vation from the ramus intestino-accessorius X. The term in- 

 testino-accessorius is used as corresponding to the nerve of that 

 name in the Urodela, but, with the absence of limbs and the 

 trapezius group of muscles, plainly most if not all of the accessory 

 eleme,nts are wanting. 



The IX-X group of nerves is simplified in the adult caecilians 

 by the absence of the lateral line contingent of the larval stages. 



