74 



VERTEBRATE SKELETON 



The squamosal is connected on its medial side with the parietal, 

 sometimes directly, but in the older groups by a supratemporal 

 bone, while in the angle between squamosal and supratemporal there 

 is occasionally a membrane bone of uncertain homology, the tabulare 

 (fig. 76), often, but erroneously, called the epiotic, the true epiotic 

 being a cartilage bone (p. 70). 



The bones so far enumerated surround the orbit, but several 

 bones may intervene between them and the eye. These bones have 



Fig. 76. — Stegocephal cranium (Capitosaurus, Zittel). eo, exoccipital; ep, tabulare 

 (epiotic); /, irontal; ju, zygomatic; la, lacrimal; 7nx, maxilla; na, nasal; o, orbit; pa, 

 parietal; pmx, premaxilla; por, postorbital; prf, prefrontal; ptf, postfrontal; qj, quadrato- 

 jugal; so, dermoccipital; sq, squamosal; si, supratemporal. 



their origin in a series of ossifications which develop around the 

 lateral Hne canals, an account of which is given in the description 

 of the Teleost skull (p. 94). In the higher groups some of these 

 lateral-line bones have received special names. The most constant 

 of these (fig. 76) are two in front of the eye, a prefrontal which joins 

 the antero-lateral angle of the frontal, and a more lateral lacrimal 

 bone, connected in many forms with the opening of the lacrimal duct. 

 The orbit is similarly bounded behind by a more medial postfrontal 

 and a more lateral postorbital bone, the latter extending to the zygo- 

 matic. Occasionally supraorbitals intervene between the frontal 

 and the orbit while there may be a similar chain of infraorbitals 

 between the orbit and the maxilla-zygomatic bar. Last to be 



