SEA-FISHERIES LABORATORY. 177 



B. — Membrane bones which have become secondarily 

 incorporated into the cranium : — 



i. Roof of Skull. Frontal (Fr.— less the fused lateral 

 line bone), Parietal (Par.). 



ii. Mouth. Ossifications in the mucous membrane — 

 Parasphenoid (Pa.S.), Vomer (Vo.). 



C. — Lateral line ossicles and bones formed by the 

 modification of such: — Lachrymal (Lc), Nasal (R.N a.), 

 Preoperculum (P. Op.), Squamosal (see pterotic — Pt.O.), 

 Suborbital chain, Supratemporal chain. 



D. — Bones formed either within or in immediate con- 

 nection with the mandibular arch of the embryo: — 

 Angular (An.), Articular (Ar. — less the fused lateral line 

 ossicle), Dentary (D. — less the fused lateral line bone), 

 Maxilla (Mx.), Mesopterygoid (Ms.Pt.), Metapterygoid 

 (M.Pt.), Palatine (Pa.), Premaxilla (P.Mx.), Pterygoid 

 (PL), Quadrate (Qu.). 



E. — Bones formed in connection with the hyoid arch 

 of the embryo : — 



i. By modification of the upper segment of the arch 

 itself — Hyomandibular (Hm.), Symplectic (Sy.). 



ii. By modification of the posterior branchiostegal 

 rays of the arch — Interoperculum (I.Op.), Operculum 

 (Op.), Suboperculum (S.Op.). 



F. — Compound bones, i.e., cranial bones to which 

 ossicles or bones originally developed in relation to the 

 system of sensory canals have become secondarily fused to 

 their superficial surface: — Articular (Ar.), Dentary (D.), 

 Frontal (Fr.), Pterotic (Pt.O.), Sphenotic (Sp.O.). 



We shall now proceed to describe the visceral skele- 

 ton proper, taking the hyoid arch first and the branchial 

 arches afterwards. 



