36 FOSSIL REPTILIA OF THE LONDON CLAY. 



and behind by an entering angle ; it is broadest behind, and from the middle of the 

 lateral border proceeds the transverse impression towards the back part of the orbit, 

 which divides the " supraorbital" scute (ob) from the " parietal" scute (pa). The occipital 

 scute is bounded laterally by straight lines, which slightly diverge as they extend back- 

 wards : there is no trace of an interoccipital scute. The parietal (pa) scute is the largest; 

 impressions of five of its borders are preserved in the present fossil : the two exterior 

 ones meet at an obtuse angle, a little above the middle of the meatus auclitorius externus ; 

 the antero-external border uniting with the postoi'bital scute (po) ; the postero-external 

 border with the external occipital scute (eo). 



In the Chelone breviceps (T. I) the frontal scute is relatively larger than in the Chelone 

 cuneiceps, and is nearly as broad as long. The sincipital scute is bounded laterally by 

 two straight lines meeting at a very open angle, from which the transverse impression 

 extends outwards between the supraorbital and parietal scutes. The straight lines 

 bounding the sides of the occipital scute diverge from each other as they extend 

 backwards more than they do in the Chelone cuneiceps. 



In the Chelone longiceps (T. Ill) a still more different pattern of the supracranial scuta- 

 tion is presented. The occipital scutes (oc) are separated by an intervening interoccipital 

 scute (io). The lateral borders of the sincipital scute are each bounded by three lines 

 and two angles ; the antero-lateral and postero-lateral angles being curved with the 

 concavity outwards ; and the transverse impression dividing the supraorbital scute 

 (oh) from the parietal scute (pa), proceeds from the middle of the intervening straight 

 border of the parietal. The frontal scute (/;•) is long and narrow, broadest behind, 

 with its lateral borders gradually converging to a point anteriorly ; the impression 

 dividing the supraorbital (ob) from the frontonasal scute (fn) proceeds from the middle 

 of that lateral border. Neither the division between the frontal and sincipital, nor that 

 between the sincipital and interoccipital scutes are well marked. 



The Chelone convexa (T. VI, fig. 4), like the Chelone longiceps, has an interoccipital 

 scute (io), and the sincipital scute (sg) has its sides bounded by three lines, of which 

 the posterior one is curved with its concavity towards the occipital scute (oc), and so 

 directed as to appear to form part of the posterior rather than the lateral border; 

 the other two lines completing the lateral border and converging forwards, are 

 divided or defined by a slight angle, from which the transverse impression pi'oceeds 

 outwards, which divides the supraorbital (ob) from the parietal (pa) scutes. The 

 frontal scute (/;•) is a small hexagon, relatively wider than in Chel. longiceps or Chel. 

 cuneiceps. The impression dividing the supraorbital (ob) from the frontonasal (fn) 

 scutes proceeds from the angle between the lateral and anterior sides of the frontal 

 scute. 



The Chelone 2)lanimentum (T. IX) is peculiar, and differs from all the foregoing species 

 by the forward extension of the occipital scutes which join the supraorbital scutes, and 

 thus divide the sincipital scute (sg) from the parietal scute (pa) ; the sincipital scute 



