SKULL — REPTILES 



145 



CHELONIA are not closely related to any other known group, 

 but such resemblances as they show point rather remotely to the 

 Cotylosaurs. The skulls are compact and are characterized by a 

 single temporal fossa, bounded by squamosal and zygomatic, a 

 quadratojugal sometimes entering the arcade. 



The chondrocranium (fig. 154) is somewhat like that of Lacertilians, but is 

 heavier and stronger. Its parts, in the known stages. He in one plane, there 

 being no marked flexure between pre- and post-hypophysial parts. The arch 



Fig. 154. — Chondrocranium of Emys lutaria, showing developing membrane bones 

 (Kunkel, '12). c, columella; cse, sphenethmoid commissure; fb, basal fenestra; //, 

 foramen lacerum; fon, orbito-nasal forainen; io, interorbital septum; ni, maxilla; n, 

 naris; nc, nasal capsule; oc, otic capsule; opt, membrane pterygoid; p, parietal; pi, 

 palatine; pm, premaxilla; po, postotic pillar; pof, postfrontal; pp, preotic pillar; prf, 

 prefrontal; pt, cartilage pterygoid; q, quadrate; sq, squamosal; ss, supraseptal plates; 

 t, posterior tectum; v, vomer; 2, zygomatic. 



of the occipital vertebrae remains separate from the synotic tectum for some time 

 and the metotic foramen is not closed above, while the foramen magnum is 

 closed by a strong process from the tectum. The basal plate has a median 

 fenestra and the plate itself narrows anteriorly to pass into the trabeculae. 

 Both hypophysis and internal carotids occupy the hypophysial fenestra, in front 

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