564 B. F. Kingsbury and H. D. Eecd. 



its more transverse course, since in Ambystoma as well as the other 

 forms examined it has a course outward, upward and also forward 

 (See, however, Siren, p. 598). The fenestral plate is at no point 

 connected with the otic capsule, at the edge of the fenestra or else- 

 where. A few sections farther forward the distal end of the stilus 

 is joined by connective tissue with the caudal edge of the palato- 

 quadrate, this junction not being as close, however, as that with the 

 squamosum. The relations of artery, vein and facial nerve are as 

 in Ambystoma (PI. Ill, Fig. 34). 



The second specimen was well along in transformation (150 mm. 

 long, gills mere stumps). At this stage the columella is connected 

 by membrane with the lips of the fenestra everywhere save on its 

 cephalo-ventral border where cartilaginous fusion has begim. Its 

 stilus is massive and abuts against the palatoquadrate with which 

 it is joined by connective tissue (PI. IV, Fig. 36, St. C). The Os. 

 pterygoideum also comes into close relation with it, but the connec- 

 tion with the squamosum existing in the larva is now much less 

 direct (Fig. 36). The characteristic inner and outer ossifications 

 are present, with accompanying changes in the cartilage. 



The floor of the ear capsule medial to the caudal portion of the 

 fenestra is nearly completely cut out as the operculum (PI. IV, Fig. 

 38, Op). In its present development, it may be compared with the 

 stage in Ambystoma shown in Fig. 32 (PI. III). An opercular 

 muscle attaches to the operculum. The recessus perilymphaticus 

 is characteristically present. 



The adult individual was 240 mm. long and was examined by 

 dissection. The condition found was much like that in the adult 

 Ambystoma. The columella, Avith its inner and outer bony surfaces, 

 the latter bearing a well ossified stilus, is completely fused with the 

 otic capsule forming the anterior boundary of the nearly circular 

 fenestra into which was fitted a cartilaginous operculum, roughly 

 hemispherical in form, its flattened surface bearing a tendon, doubt- 

 less that of the M. opercularis, which was not, however, dissected 

 out. Fusion with the otic capsule was apparently by cartilage only, 

 so that, by the use of some force, the stilus and plate could be and 

 were completely broken away. The distal end of the stilus was con- 



