HYOBRANCHIAL APPARATUS OF SPELERPES 539 



2. Hyobranchial muscles 



The hyobranchial muscles of the adult also show a delicacy 

 and complexity, well adapted to the great mobility of the region. 

 I find in them a marked correspondence, in all but a few compara- 

 tively unimportant details, to the muscles of the European 

 species Spelerpes (Geotriton) fuscus, as described in 1875, by 

 Wiedersheim who designated the various muscles merely by 

 letters, as he had not the morphological data to name them. As 

 they also resemble the muscles of the adult Salamandra maculosa 

 described by Driiner in 1904, and as I have traced their devel- 

 opment through metamorphosis, I now attempt to give them 

 their morphological names. Figures 19 and 20 show them from 

 more superficial and from deeper ventral dissections, respec- 

 tively, and figure 21 pictures a pharyngeal (dorsal) dissection. 

 Figures 22 to 27 show important levels in cross-section. 



The intermandibularis anterior arises from the inner surface 

 of the mandible and is like the larval muscle, except that the 

 median raphe, which in the larva is scarcely indicated, is now 

 broad and definite. 



In the position of the intermandibularis posterior of the larva 

 there appear two distinct muscles. Whether these together are 

 the morphological equivalent of the larval muscle, or whether 

 only the more anterior one represents it, and the more posterior 

 is a new muscle which develops at metamorphosis, I cannot at 

 present state, though the latter view is the more probable. The 

 more anterior of these muscles, the interhyoideus (interossa- 

 quadrata of Driiner) arises from the distal end of the ceratohyal 

 near its attachment to the quadrate bone, but not from the latter 

 bone, as Driiner 's name suggests; spreads out like. a fan, and is 

 inserted on the median raphe. The more posterior, (Driiner's 

 quadrate-pectoralis) curves around the throat in a posteromedial 

 direction, from .just beneath the dorsal integument and is in- 

 serted in the gular fold. As I can find in it no relation either to 

 the quadrate bone or to the pectoralis muscle, and as it seems so 

 clearly to be an integumental muscle regulating the gular fold, 

 gularis might be a better name for it. 



