Chap. m. GENERA AND SPECIES OF CHELONIOID^. 377 



I. CiiELONiA, Browjn. {Fitz.) 



The genus Clielonia, when first separated from Testudo bj A. Brongniart, 

 included all the marine Turtles, even Sphargis. It was next limited to the 

 Chelonioida3 proper, and in this extension it corresponds exactly to Merrem's 

 genus Caretta. Now it embraces only the green Turtles. It was first restricted 

 to its present limits by Fitzinger.^ 



The head of this genus, thus limited, is high, and continues so forward to 

 the frontal region, where the upper surface descends steeply to the nose. From 

 the nose down, the outer surfoce of the end of the bill of the upper jaw is 

 curved outward ; but it is turned back as far below as above. Tiie mouth is 

 long, but broadly curved at the front end. The alveolar edge of the bill of the 

 upper jaw is straight, or slightly concave at the sides, and slightly notched at the 

 front end ; it is sharp, but not serrated. The vertical inner surfiice is broadest 

 at the hind end, and narrows thence forward till at the front end a small pit 

 in the palate again widens it. The outer edge of the horny roof descends from 

 behind forward to the pit above mentioned ; the surface within descends from this 

 edge inward to a ridge, which ridge has a deep depression at the symphysis, 

 is most prominent on each side of the depression, and decreases thence backward. 

 The space between: this ridge and the outer wall is a furrow, into which the lower 

 jaw fits, as well as into the pit in front. Within this ridge the surface is broad, 

 and also has a depression at the symphysis; this surface descends to a small ridge 

 at its irmer edge. The lower jaw is highest at the angle, and foils thence for- 

 ward, but at the front end there rises a small, sharp projection. The alveolar 

 edge of this jaw is deei:)ly serrated. Within this edge is a furrow, correspond- 

 ing to the ridge of the upper jaw, which is widest at the symphysis, and there 

 divided by a transverse ridge ; it is deepest on each side of that ridge, and fiides 

 out shortly before reaching the angle of the jaw. The ridge on the inner side 

 of this furrow does not descend from behind forward as fast as the outer alve- 

 olar edge, and at its front end is as high as the latter ; it rises at the sym- 

 physis to a sharp tooth, which is, however, almost entirely formed from the 

 horny covering. The ridge vanishes with the furrow backward. Its inner surface 

 descends a little way, in one slope, and then more steeply to the attachment of the 

 tongue. The outer alveolar edge of this jaw is serrated as far back as the hind 

 angle of the jaw. When the mouth is closing, this edge approaches the alveolar 



* Syst. Rept. 1843. It is adopted by .1. E. Gray, Tschudi, in liis Fauna peru.an.a, 184o: but Tscliudi 

 in the same extent, Cat. Brit. Mus. 1844, and by proposes to change the name to Euchelonia. 



48 



