[49] THE OSTEOLOGY OF AMIA CALVA. 795 



''Jlithertoit has beeu currently stated in anatomical text--books that 

 the mento-meckelian bone at the distal end, and the articular bone at 

 the proximal end of Meckel's cartilage, were the only elements of the 

 mandible really formed by ossification of the cartilage itself, yet in 

 Amia there can, I think, be but little doubt that at least four, and 

 probably five, ossitic centers are developed in the axial cartilage. 

 Whether one of the centers a, b, c, and d represents the os articulare 

 of the Teleostean mandible, or whether the latter bone is really a com- 

 pound bone resulting from the coalescence of the persistently distinct 

 elements of Amia, is not very evident ; but I am inclined to think that 

 the OS articulare is not so simple a bone as it has hitherto been supposed 

 to be. As the Meckelian cartilage is the distal, or ventral half of the 

 first postoral visceral arch, though it may not be possible to point out 

 the special homologies of the mento-meckelian, and the ossicles a, &, c, 

 and d, with the ossifications found m the ventral halves of the remain- 

 ing postoral arches, yet I think that we may roughly correlate those 

 ossicles with the interhyal, epihyal, ceratohyal, and hypohyal of the hy- 

 oidean series." 



" It may also be that the cartilaginous ' coronoid process ' is another 

 instance of the tendency manifested by the first postoral arch ta develop 

 forward connective outgrowths, of which the orbitar process and the 

 palato-pterygoid arcade are conspicuous examples in the proximal half 

 of this arch. In addition to the mandibular elements above referred to 

 there are, in addition, several membrane bones. The ossification a has 

 a small ganoid plate {d. af^ attached to it, which appears at the extreme 

 tip of angle of the jaw." 



I show in Plate Y, Fig. 18, the large triangular splenial in situ. 

 This bone does not run out to the symphysis of the rami anteriorly, but 

 is indirectly connected with it on either side through a chain of five 

 very much smaller plate-like bones. These each support a tuft of good, 

 strong teeth, and very much remind one of the dental plates arranged 

 along on the superior aspect of the branchial arches. I am surprised 

 that Bridge did not notice this when he compared the numerous ossifi- 

 cations of Meckel's cartilage with these arches, as the simile is equally 

 striking. Teeth are found also over quite an extensive area on the 

 upper part of the splenial, though here they are very fine indeed (Fig. 

 18). When the splenial is in position, a large subcompressed conical 

 space is inclosed between it and the outside bones. - The base of this 

 cone is directed inwards and forihs the opening lo the sulcus in ques- 

 tion. Both the symplectic and the preoperculum contribute to form the 

 cup for articulation with the mandible, and the quadrate supplies an ar- 

 ticular semi- globular head for the same purpose. As already described, 

 the opposed surfaces on the jaw are developed from special ossific cen- 

 ters. 



''This is the ossicle marked s in Fig. 16 of this paper 



