Plate II. 



Drawings of models of the ear region of the skull. 



Fig. 25. Ambystoma punctatum, adult. A portion of the ear region of 

 the skull showing the completely fused columella and the fully formed oper- 

 culum with its attached muscle. 



Fig. 26. Salamandra maculosa, adult. The region and aspect as in Fig. 

 25 with which it may be directly compared. The boundary between muscle 

 and operculum is indicated by the broken line. 



Fig. 27. Triton cristatus, larva 34 mm. long. The ventro-lateral aspect 

 of the cartilaginous ear capsule. The cephalic part of the fenestra is occu- 

 pied by the small and partially fused columella above, a growth of cartilage 

 below. The operculum is still broadly joined to the ear capsule. 



Fig. 28. Typhlomolge rathbuni, adult. Lateral aspect of the ear region. 

 Attention is particularly called to the segmented (fragmented) stilus colu- 

 mellse and its relation to the facial nerve (ramus jugularis). 



