SOUND-TRANSMITTING APPARATUS OF CAUDATA 



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represents a secondary relation. From the morphological view- 

 point this connection is one of the most important structures of 

 the whole sound-transmitting apparatus in the Plethodontidae, 

 Desmognathidae, and others. For this reason and for the sake 

 of easy reference later, it will be termed the isthmus fenestralis. 



Fig. 1 Transection through the fenestra vestibuli of an adult Spelerpes bis- 

 lineatus at the level of the stylus columellae. C.I., canalis lateralis; Col., stylus 

 columellae (columella); Ec, ear capsule; Fe.m., fenestral membrane; Op., fenes- 

 tral plate representing the operculum; Sq., squamosum. 



