CHELONIDAE 



379 



and the prefrontals. The choanae are enclosed by the palatines, 

 which are separated by the vomer, and are posteriorly in broad 

 contact with the pterygoids. The latter are connected with 

 descending processes of the parietals by epipterygoids. The fora- 

 men magnum is bounded not only by the supra-occipital and the 

 lateral occipitals, but also by the basi-occipital. For the skeleton 

 see Fig. 65, p. 320. The pubic and ischiadic symphyses are con- 

 nected by a narrow cartilaginous band. The pubis has a large, 

 broad, lateral process, but the ischium is devoid of such a process. 



Fig. 84. — Skull of Thalassnchelys caretta ; cf. also Fig. 63, p. 317. ^4, Dorsal view ; 

 B, ventral view ; F, froutal ; Jg, jiigal ; Mx, maxillary ; Op, opisthotic ; P, 

 parietal ; Pal, palatine ; Pr.f, prefrontal ; Pt.f, postfrontal ; Ptg, pterygoid ; Q, 

 quadrate ; Quadr, articular surface of quadrate ; Qj, quadrato-jugal ; S.o, supra- 

 occipital ; Sq, squamosal. 



The paddles of the fore- and hind-limbs are produced by an 

 elongation of the metacarpal and metatarsal bones and of most of 

 the phalanges, and these have no condyles ; most of the carpal 

 and tarsal elements are flattened, and additional width is given 

 to the hands by the much enlarged pisiform bone. The number 

 of phalanges of the five fingers is 2, 3, 3, 2, 2 ; that of the five 

 toes, 2, 3, 3, 3, 2. 



The carapace is heart-shaped and very flat. The nuchal plate 

 has no rib-like processes. The eight neurals form a continuous 

 series, and the short tail is covered by two or three pygal plates 

 liesides the unpaired last marginal. The number of all the 



