No. I.] SKELETAL ANATOMY OF AMPHIUMA. 29 



we find both nerves on the outside of the descending processes, 

 and yet these processes have undergone no change, except that 

 they have approached each other more closely. These parts 

 may undergo some modifications by the time the animal has 

 reached adult size, so as to justify the distinguished author's 

 description, and his Fig. 20, Tafel II ; but it seems more 

 probable that he has been misled by not having closely consec- 

 utive sections. With my sections the thousandth of an inch in 

 thickness I have no difficulty in making out the changes in 

 position of the processes. It would almost appear that in the 

 process of lengthening which the snout has undergone the 

 orbitosphenoid and the cartilaginous internasal septum have not 

 been able to keep pace with the other structures, and that their 

 deficiencies have had to be made good in the one region by an 

 extraordinary development of the frontals and in the other by 

 the production of the perpendicular plate of the premaxillary. 



Dr. Wiedersheim {op. cit., p. 136) states that "das cartilagi- 

 nose Operculum zu einem kurzen ebenfalls knorpeligen Stiel 

 auswachst," etc. My specimen, young as it is, tells a different 

 story. The rim of the operculum is wholly cartilaginous ; but 

 both the inner and the outer surfaces of the central portion of it 

 are converted into bone. The head of the columella is coossi- 

 fied to the centre of the operculum ; but almost immediately 

 after it has freed itself, the columellar rod becomes cartilagi- 

 nous. The thickened lower border of the squamosal then de- 

 scends upon the columella, and is continued upon it to a point 

 somewhat in front of the fenestra ovalis. Here this rod once 

 more becomes surrounded by bone, which passes forward into 

 that of the quadrate. Sta. in Fig. 10 points to the bone- 

 incrusted operculum. From the anterior bony portion of the 

 columella a broad process of bone rises up between the squa- 

 mosal and the otic capsule ; and this may be traced backward and 

 upward for some distance, until at length it ends in a point. 

 The termination of this point may be seen in Fig. 10, Co.p. 

 For a part of the way anteriorly this process rises nearly to the 

 upper border of the squamosal. Such is seen to be the case in 

 Fig. 9, which passes through the foramen for the facial nerve. 

 Here the axis of the columella is seen to be cartilaginous, but 

 surrounded by bone which passes into a plate lying inside the 

 squamosal. We might say, in other words, that the quadrate 



