JO B. F. KINGSBURY. 



the entire quadrate cartilage, with the exception of the articular 

 surfaces, has become ossified, with the formation of a marrow 

 cavity, and the primary ossification, bone " x," is no longer dis- 

 tinguishable as a distinct structure. In how far this same mode 

 of ossification prevails among Urodela, I cannot say, but I believe 

 from examination of Amblystoina, Ainphinma and Desmognathus, 

 quite generally. 



A cartilaginous process of the quadrate is quite generally found 

 in Urodela extending forward toward the antorbital process of 

 the chondrocranium, forming a " pterygoid arch "(?). Its absence 

 in Nccturus is noteworthy. It is also absent in the larva of Spcl- 

 erpes, and I believe, most larval urodeles, developing at transfor- 

 mation. Examination of the sections strongly suggested that in 

 both larval Spclerpes and Nectums, it was present in a " pro -car- 

 tilaginous " form. 



The Nasal capsule in Nectiirus (and Proteus] is quite unique, 

 fenestrated, thin, imperfect, without cartilaginous or bony con- 

 nection with the chondrocranium. In the larval Spclerpes it is 

 absent, developing at transformation. 



In the lower jaw, there are comparisons of interest. Briefly 

 stated, the mandibles of Nectnnis and of the larval Spclerpes are 

 directly comparable. Each consists of three bones, dentare, oper- 

 culare (spleniale ?), and angulare together with Meckel's cartilage. 

 The angulare seems slightly fused with the articular head of 

 Meckel's cartilage in both Nectums and the larval Spelerpes. It 

 extends back, forming the "angle" of the jaw, and to its caudal 

 end attaches the mandibulo-hyoid ligament. In the adult Spel- 

 erpes this bone and the head of Meckel's cartilage are coosified, 

 forming one bone, which perhaps should be termed articulo- 

 angulare, though I believe that the ossification proceeds from the 

 angulare and is at first distinct from the cartilage, in a manner 

 entirely comparable with the ossification of the articular end of 

 the quadrate cartilage. The operculare, a bone present in larval 

 and absent (always ?) in adult gill-less life, is, interestingly enough, 

 present in Necturus. As to its fate in the adult (gill-less), there 

 is at present, I believe, no satisfactory evidence. I do not believe, 

 however, that it becomes fused with the angulare. 



The statements of the relation of muscles, ligaments and nerves 



