The Amphibian larynx. 313 



lethra (Fig. 61) appears very simple, divided into four quarters by 

 median and lateral raphes. The lateral raphes appear to be con- 

 nected with the method of insertion of the Dilatator, and suggests 

 again the problem mentioned in the consideration of Triton, as to the 

 reality of the Sphincter laryngis of Göppert, as an element distinct 

 from the Laryugei. Whether the condition of these muscles in Fipa 

 resembles that of Bactylethra I cannot say, as Grönberg's description 

 is insufficient to determine. Farther investigation of this point is 

 much to be desired. 



4, Summary of Part II. 



1. The Pharyngo-branchial musculature of the Amphibia may be 

 reduced to a simple series, corresponding to the visceral arches and 

 consisting each of a dorsal and a ventral segment. 



2. The laryngeal musculature of the Uro delà is derived from 

 elements of the last two visceral arches, the extrinsic ele- 

 ments being furnished by the muscles of the 6^^ arch (Dg and Vq) 

 and the dorsal segment of the 7t'> arch (D7); and the intrinsic 

 elements derived from the ventral segment of the T'h arch (F^). 



3. In the Anura the elements of the 6'^ arch disappear, and 

 the entire musculature is furnished by the elements of the 7'^ arch, 

 the extrinsic from the dorsal segment, and the intrinsic from 

 the ventral. 



4. The elements of the 6'^ visceral arch possess only an oc- 

 casional relationship to the parts of the larynx and may consist of 

 the ventral segment alone, in cases where the 4th giU-arch is deve- 

 loped, or of both dorsal and ventral segments separated by a tendi- 

 nous rudiment of the gill- arch, in which case the muscle is known as 

 the Digastricus pharyngis (Göppert). 



5a. The dorsal segment of the 7*^ visceral arch forms 

 the real extrinsic laryngeal muscle, and is partly or wholly 

 designated as either Dorso-trachealis or Dorso-laryngeus, 

 according to its place of insertion. In the Anura this element is 

 divided by the thyroid process of the hyoid complex into a dorsal 

 portion, the posterior Petro-hyoideus, and a ventral portion, the 

 Dilatator laryngis. 



b) The ventral segment of this arch forms the intrinsic 

 laryngeal system, and consists primarily of two pairs of Laryn- 

 gei, which may secondarily form a ring about the orifice of the 

 glottis, termed the Sphincter laryngis. Although by the re- 



