No. I.] SKELETAL ANATOMY OF AMPHIUMA. 25 



ward from one-third to one-half the distance to the middle line. 

 On this shelf is supported the trigeminal and facial nerve 

 ganglia. With the central band of cartilage have disappeared 

 also all traces of the notochord from the base of the skull. 



The prootics are quite thoroughly ossified. Two points, how- 

 ever, as Wiedersheim has observed, even in the adult, remain in 

 a cartilaginous state, viz. : those to which are articulated the ped- 

 icle and the otic process of the suspensorium. A broad band of 

 cartilage, running transversely through the otic capsule in the 

 region of the fenestra ovalis, separates the prootic from the 

 opisthotic. The latter send inward toward the middle line each 

 a process of bone which grows wider as we proceed backward. 

 These, however, nowhere come into contact, but are connected 

 by a considerable basioccipit'al cartilage. 



The foramen magnum is bounded above by the opisthotics, 

 which for a short space come into contact in the middle line. 

 More anteriorly, beneath the hinder ends of the parietals, the 

 opisthotics are separated by a mass of cartilage which may be 

 regarded as the supraoccipital. 



The inner wall of the auditory capsule is well ossified. In 

 this inner wall I find anteriorly a foramen for the branch of the 

 auditory nerve, which is distributed to the upper portions of the 

 labyrinth. Further back, a much larger branch of the auditory 

 nerve enters the labyrinth through about three closely placed 

 foramina, and is distributed to the sacculus and probably the 

 lagena. On the inner wall of the sacculus, we find a laree 

 macula, and immediately outside of this a very large otolith. 

 {See Fig. 10, Ot) This otolith reminds us of that of some of 

 the fishes. The opening for the escape of the ductus endolym- 

 phaticus is situated at the upper border of the wall immediately 

 above the foramina for the saccular branch of the auditory 

 nerve. Just behind the last-mentioned foramina is an opening 

 in the cartilage, as in the larva, through which I have supposed 

 a lymph sinus to pass. This foramen lies just mesiad of the 

 lagena. 



The ossification of the trabecula lying mesiad of the prootics 

 is carried forwards, anterior of the foramina for the escape of 

 the fifth nerve. It soon, however, becomes reduced to a mere 

 shell of bone surrounding the cartilage. Then begins the orbito- 

 sphenoidal bone. This is more or less completely ossified as 



