No. I.] SKELETAL ANATOMY OF AMPHIUMA. ij 



outer border, and between the antorbital cartilage and the tri- 

 geminal foramen, is a slender club-shaped tract of cartilage, whose 

 position is shown in Fig. 4, Pt. It appears to represent the 

 pterygoid cartilage of other Urodeles ; but it has not yet formed 

 a connection with the suspensorium. It lies about its own 

 diameter outside of the trabecula. 



The eye is wholly devoid of any cartilaginous capsule. 



Another cartilage that I have sought for with great interest is 

 that which appears in the roof of the mouth of the adult, in 

 front of and between the anterior ends of the vomers and below 

 the palatine process of the premaxilla. Not a trace of this car- 

 tilage is seen in any sections that I have examined. 



The floor of the brain-case just described is concave from side 

 to side. Proceeding forward from the foramen magnum, the 

 floor, as shown in a longitudinal section along the middle line, 

 slopes rapidly down beneath the hind-brain, then horizontally 

 forward to the middle of the cerebrum, where the slope is again 

 upward. 



Coming to the post-oral structures, we observe first that 

 Meckel's cartilage comes forward and meets its platetrope, 

 while posteriorly it projects behind the articulation with the 

 suspensorium, and gives insertion to the digastric muscle. This 

 cartilage is ensheathed by membrane-bones, which will be con- 

 sidered further along ; but it shows no signs of a deposit of 

 calcific matter to form the articular. 



The suspensorium (Fig. 4) is of a quadrate form, is directed 

 slightly forward, and in transverse sections is broader below 

 than above. It articulates with the auditory mass by means of 

 the otic process and the pedicle. Starting from the lower end 

 and inner border of the suspensorium is the long and slender 

 ascending process, which runs upward and forward, and co- 

 alesces with the cranial wall at the anterior side of the trisfemi- 

 nal foramen. I find no trace of a pterygoid process. From the 

 hinder border of the suspensorium (Fig. 4) starts out a short 

 process which articulates with the columella auris. No ossifica- 

 tion has as yet appeared in the suspensorium. 



The columella is a short rod of cartilage, which, articulating 

 with the suspensorium anteriorly, runs backward and coalesces 

 with the outer surface of the stapes. Its relation to the facial 

 nerve will be discussed later. 



