No. I.] SKELETAL ANATOMY OF AMPHIUMA. jq 



{Kopfskclct dcr Urodclai) seems to have been the first to de- 

 scribe correctly this structure, especially the relation of the 

 palatine process to the premaxilla. He endeavors to explain 

 this remarkable bone by suggesting that we have in it a com- 

 posite of morphologically different elements. In the ascending 

 and the alveolar portions of the bone there is supposed to be 

 the proper premaxillary. In the osseous nasal septum and pal- 

 atine process we have an ectosteal {perichondrostotiscJi) bone 

 formed from the originally hyaline nasal septum, which bone 

 has become confluent with the proper premaxillary. The fact 

 that the parasphenoid pushes itself between the ethmoidal car- 

 tilage and the posterior end of the palatine process causes Dr. 

 Wiedersheim to suggest a doubt as to the correctness of his 

 own theory ; and he says that amid these doubts nothing will 

 clear up the difficulty except a knowledge of the embryology 

 of this Urodele. 



In my specimens the premaxillary is already well ossified ; 

 and there is, even in this early stage, no trace of any original 

 separation into two centres. The alveolar processes are long 

 and comparatively strong. Situated on their border is a number 

 of teeth, eleven, as I count them, one being accurately in the 

 middle line. An examination of the adult in my possession 

 shows that it has the same number and arrangement of the 

 teeth. In the young this median tooth, and one on each side 

 of it, are especially large, sharp-pointed, and directed nearly 

 backwards. There are long ascending and palatine processes, 

 although, as might be expected, they do not extend so far back- 

 ward as in the adult. The palatine process reaches back nearly 

 to the point where the trabecular cornua diverge from each 

 other. It has no connection with any cartilage, and there is at 

 this stage no cartilaginous nasal septum. It seems quite evi- 

 dent, therefore, that the premaxillary is not a composite struc- 

 ture, but that the palatine process continues to grow backward 

 as a membrane-bone until it attains the dimensions that it has 

 in the adult. 



As has already been stated, the anterior lobes of the trabec- 

 ular cornua, like a divided prenasal process, end in the angle 

 between the alveolar and the palatine processes quite close to 

 the lower border of the latter, and close to one another. To 

 me it now appears quite probable that these cartilages grow 



