MEMBRANE BONES OF SKULL 



577 



that their homology is difficult, especially m the various groups 

 of fishes. There are, however, no dermal bones in the skulls of 



LnttTitm^ordL 



B 





postfiarictil. 

 — Ca.LruLa.T 



D 



t al/uLi-r 



Fig. 440. — Diagrams of the main types of reptilian skulL A, anapsid ; B, synapsid ; 

 C, parapsid ; D, diapsid. The facial portion of the skull, shown only in A, is 

 the same in all types ; the nasal foramen, the orbit, and the temporal vacuities, 

 are shown in black. 



FR, frontal; /, jugal ; LAC, lacrimal; MX, maxilla; NA, nasal; PAR, parietal; FMX, premaxilla; 

 PO, postorbital(s) ; POF, postfrontal ; PRF, prefrontal ; Q, quadrate ; QJ, quadratojugal ; SQ, 

 squamosal. 



fishes which cannot be traced in tetrapods, except for the gulars 

 and operculars — series of bones which support the operculum. 





Fig. 450. — The skull of a turtle.— From Thomson. 

 AN. Angular; AR, articular; D. dentary ; FR. frontal; /. juji..! ; MX, maxilla: /'/•-. profronta! ; PAR, 

 parietal ; PMX, premaxilla ; PGF, postorbital fused wim prefront..! ; Q, quadrate ; (,) I . quadrato- 

 jugal ; 5, surangular ; SO, supraoccipital ; SQ, squamosal. 



The skull of the cod, which has a fairly complete series of bones, 

 is shown in Fig. 448. 



