SKULL — REPTILES 



143 



of the Meckelian, usually fusing early with the articulare. The 

 number of these bones is often reduced by fusion in the adult, some- 

 times by absolute loss. 



The hinder of the visceral arches are reduced or absent in the 

 adult, while the anterior branchials are more or less closely connected 

 with the body of the hyoid. The adult Chelonia are the more 

 primitive in retaining three independent arches (hyoid and first two 

 branchials) the latter connected with the hyoid body. The arches 

 may persist, in part, as cartilage, part being ossified. There are two 



Fig. 152. — Theromorph skulls: A, Seymouria (Williston) ; B, Pantyltis (WiWiston); 

 C, Cynognathus (Gregory); an, angulare; ar, articulare; d, dentale; do, dermoccipital; 

 /, frontal; /, lacrimal; 7nx, maxilla; n, nasal; p, parietal; pf, pof, postfrontal; pm, pre- 

 maxilla; po, postorbital; pr, prefrontal; q, quadrate; qj, quadratojugal; 5a, surangulare; 

 sq, squamosal; si, supratemporal; t, tabulare; z, zygomatic. 



parts to the hyoid, cornua and body, and the relations of the former 

 in Crocodiha support the view that a part of the ossicula auditus of 

 reptiles (and probably of other Amniotes) has been derived from the 

 hyomandibula (p. 119). 



THEROMORPHA. — Division of reptiles into Synapsida and Diapsida (p. 

 138) separates the Pelycosaurs from the other forms, but for convenience all are 

 treated here together. Only a few general statements are made here; reference 

 must be to special papers for details. All Theromorphs have short, broad crania, 

 usually with a parietal foramen, and beyond this opening and the orbits and 

 nares, the roof is complete in Cotylosaurs (fig. 152), while in Therapsids there is a 

 single temporal fossa bounded laterally by a squamoso-zygomatic arcade, 

 which may also include the postorbital and the quadratojugal when the latter 



