SKULL— TELEOSTOMES 



97 



Most of the rest of the Meckelian remains cartilage or is resorbed, 

 but some Ganoids have a mentomeckelian developed on either side 

 of the symphysis. The other bones of the lower jaw are dermal in 

 origin, the most constant of these being a large dentale, usually 

 toothed, and an angulare on the posterior and inferior parts of the 

 jaw. Some Teleostomes have a splenial (two in Amia) on the medial 

 side of the jaw, this occasionally bearing teeth. There is sometimes 

 a strong coronoid process on the upper margin of the jaw for the 

 insertion of the occludent muscles, and there maybe a separate coro- 

 noid bone. Many fishes have a bone (sesamoid articulare) closely 



Fig. 103. — Pterygoids, suspensor and operculum of Scomber (AUis, '03). e7ip, 

 entopterygoid; ep, ectopterygoid; hm, hyomandibula; io, interoperculum; mtp, meta- 

 pterygoid ; op, operculare ; pi, palatine ; po, preoperculum ; q, quadrate ; sop, suboperculum ; 

 sy, symplectic. 



associated with the MeckeUan, apparently an ossification of the 

 tendon of the adductor mandibulae muscle. 



With ossification, the hyomandibular cartilage becomes two bones, 

 an upper hyomandibula and a lower symplectic which connects with 

 the quadrate. The hyale and branchial arches usually ossify directly 

 without any membrane bones, but such sometimes occur. The 

 extent of these ossifications varies greatly. The basihyal may extend 

 in front of the hypohyals which it connects as a strong OS entoglos- 

 sum fglossohyal), a part of which may come from a possible mandi- 

 bular copula (p. 86). In several fishes 'the posterior side of the 

 basihyal is connected with a vertical plate, the thyreohyal, which 

 gives attachment for the retractor muscles of the hyoid apparatus. 

 The rest of the copular structures varies considerably, that of the 



