304 H. H. WILDER, 



which spreads out fan-like over the lateral walls of the trachea '). 

 Its reversed ])osition relative to the Hyo-})haryngeus, which occurs 

 in Siren, has already been i)ointed out. In Menopoma the Dorso- 

 t r a c h e a 1 i s forms a wide band arising almost from the mid-dorsal 

 line. This band runs beneath the ligament of origin for a portion of 

 the Hyo- pharyngé us, and is inserted into the upper part of the 

 trachea, in the region of the small and irregular nodules of cartilages 

 referred to in Part I (Figs. 15 and 16). The anterior fibres of this 

 muscle form a narrow band which runs up to the arytaenoids in which 

 it becomes inserted. In Siredon, Dorso-laryngeus appears en- 

 tirely distinct from Dorso-trachealis, and runs beneath the latter 

 muscle (Fig, 22). The condition in Triton may be possibly a modi- 

 fication of this, in which the Dorso-trachealis is entirely sup- 

 pressed. Here a delicate band, arising from the skull near the origin 

 of the Digastricus pharyngis, becomes inserted into a lateral 

 knob on the arytaenoid cartilage (Figs. 27—30). This is evidently 

 a Dorso-laryngeus, but whether it has resulted from a loss of 

 the tracheal portion, or from a fusion of both, cannot now be de- 

 termined. 



c) Intrinsic system. 



This consists of the Laryngei (Göppert) represented in the 

 Proteidae by two pairs of fan-shaped muscles lying upon either side 

 of the Cartilago lateralis and distinguished as dorsal and ventral. 

 The question of the origin of these has been discussed previously, 

 and can be fully decided only by embryological investigation. 



In the other Ichthyoid Urodeles (Siren, Menopoma etc.) the 

 Laryngei arrange themselves more in the form of a ring, divided into 

 four quadrants, laterally by the arytaenoid cartilages and medially by 

 raphes. This symmetrical disi)osition of the ring and the position of 

 the cartilages led me to suggest the theory presented in my paper of 

 1891 on Siren lacertina (No. 11), a theory which I abandoned for 

 the present one in 1892 (No. 12). 



The Salamandridae possess a muscular laryngeal ring apparently 

 similar to that shown in the lower forms, but lying in a ditierent 

 l»lane. Here the ring has rotated in such a way that the cardiac or 



1) The "Depressor laryngis", a muscle described in my 

 paper on Siren is a portion of the Dorso-trachealis continued across 

 the ventral side of the trachea. The fibres from the two sides do not 

 interlace, but one layer overlaps the other. 



