300 H. H. WILDER, 



however, we compare this section with Fig. C of the present work, 

 we may interpret this inscription as the rudiment of the little car- 

 tilaginous piece formed by the projecting lateral hook of the Cartilago 

 lateralis (i. e. the ö'h branchial arch) or else as the ligament extend- 

 ing posteriorly from this (see Fig. 24 *). 



In the section in question, this ligament is seen to separate the 

 Dorso-laryngeus (D^) from the two Laryngei (F^) in the same manner 

 as the two elements of the preceding visceral arch (Dg and Vq) an 

 separated by the rudiment of the 4'^ epibranchial. 



A similar relationship in the case of the larval Salamander is 

 shown in fig. 8 of Göppert's work. 



3. The respiratory muscular system of the other ürodeles. 



a) Introduction. 



If we may base our homologies of the respiratory muscles upon 

 the plan above given, considered as primitive, we see that the mus- 

 cular elements of the 7*^ visceral arch (= respiratory cartilages), are 

 the only ones originally connected with the system. The muscles of 

 the 6'^' visceral arch (4^^ branchial) will be found in a few cases to 

 be connected with the respiratory cartilages, a condition which we 

 must interi)ret as secondary, and the muscles of the 5th visceral arch 

 possess only a topographical relation. This may be expressed by the 

 following table: 



5th visceral arch {d^^ branchial). 



Dorsal segment: The Levator arcus III of Urodeles. Here 

 referred to as Dorso-branchialis 3 (D^). 



Ventral segment: This is Pharyngo-branchialis 3 ( F5) of 

 the diagram. It is present only in the Proieidae and forms the 

 anterior i)ortion of the broad })haryngeal sheet. It was confused by 

 GöppERT with the next posterior muscle , Pharyngo-branchialis ^ 

 (Fe) under the name of Hyo-i)haryngeus. It is absent in other 

 Urodeles and never serves as a laryngeal muscle. 



6th visceral arch (4th branchial). 



The cartilaginous arch is present in the adult in a few forms 



only (Siren, Amphiuma etc.). In the Proteidae and in the higher 



Urodeles it is represented by a tendinous inscription seiiarating 



the two muscular segments, which thus become a single digastric 



