THE SKULL OF REPTILES 1 7 



Ichthyosauria (Fig. 50). Thought by some to be the homologues of 

 the mammahan lacrimals, and so called. 



Postfrontals (pf). Primitively (Figs. 2,4, 22) at the upper posterior 

 border of the orbits, articulating with prefrontals, frontals, parietals^ 

 the intertemporal or supratemporals when present, and with the 

 postorbitals. 



In the Chelonia (Figs. 30 a, 31 b, c, 32 a), Crocodilia (Figs. 68, 

 69), many mosasaurs (Fig. 54), lizards (Fig. 56) and the snakes 

 (Fig. 59), the Pterosauria (Figs. 71, 72), Dinosauria (Fig. 70), and 

 many Therapsida (Figs. 44 d, 45), they are absent or fused with the 

 postorbitals which take their place. Sometimes they (Fig. 46 c, 49 a) 

 help form the anterior boundary of the upper temporal opening. 

 They extend forward to the nasals in the Ichthyosauria (Fig. 50). 



Postorbitals (po). Primitively (Figs. 

 2, 3, 4, 5, 22) at the upper back part 

 of the orbits, articulating with post- 

 frontals, jugals, and squamosals. A 

 descending process also articulates 

 with the maxillae or ectopterygoids. 



In the absence of the intertemporal 

 and supratemporal, the postorbital Fig. 5. p««/y/«.f. Cotylosaurskull: 



, . , • 1 .1 • 1 /T^' left temporal region, from without. 



also articulates with the parietal (I IgS. Three fourths natural size. 



28, 30, 33, 43). In the absence of the 



postfrontal it takes its place, often extending forward to meet the 

 prefrontal (Figs. 30, 45 b), or even the lacrimal (Fig. 70 a) in the 

 Theropoda. It still retains its connection with the maxillae [sic] ^ in 

 certain Chelonia (Fig. 31 b) and most snakes (Fig. 59), but not in 

 most other reptiles. Rarely in the lizards (Fig. 56) it does not meet 

 the squamosal. In the Crocodilia (Fig. 69) it is large, and may ar- 

 ticulate with frontal, parietal, jugal, quadratojugal, and squamosal. 

 It extends far back in the Chelonia (Figs. 30, 31 a), forming a large 

 part of the temporal roof, articulating with the quadratojugal, the 

 latter also in the Ichthyosauria (Fig. 50). It is extensive also in 

 some of the Dinosauria (Fig. 70), supporting the paired horns of 

 the Ceratopsia (Fig. 70 d). 



Jugals ijii). Primitively (Figs. 2 b, 3, 5, 22, 33) large, forming the 

 under boundary of the orbits, articulating in front with lacrimals 



1 ["Maxillae" — a lapsus calami for "parietal"? — Ed.] 



