166 BRITISH FOSSIL REPTILES. 



having the upper surface traversed by two longitudinal furrows, slightly converging 

 as they approach to the point. The outer or alveolar borders are obtusely rounded ; 

 and are perforated, as in most Chelonians, by a series of small vascular foramina : the 

 rounded border increases in breadth as it extends backwards where it is continued 

 upon, or forms, the outer surface of the beginning of the ramus of the jaw. The com- 

 mencement of the coracoid process rises from the inner border of the ramus which is 

 continued from the hinder and upper border of the broad symphysis. In this 

 character, also, the present mandible differs from all that I have previously seen, 

 either fossil or recent. In its general form it resembles, like some of those from the 

 Bracklesham Clay, the mandible in the Trionycida, rather than that in the existing 

 Chelones. The specimen is in the Collection of James S. Bowerbank, Esq., F.R.S. 



In the same rich depositary of British Fossil remains is the portion of a Chelonian 

 mandible, PI. 48, figs. 6 and 7. It has formed part of a longer, narrower, and more 

 pointed lower jaw than the one above described. The bony symphysis is much 

 shorter ; the rami longer, deeper, and more regularly convex on their outer side. It 

 thus, likewise, presents the characters rather of a Triont/x than of a modern Chelone ; 

 but the modifications of the lower jaw, in indubitable species of true Turtle from 

 the older Tertiary deposits, forbid a conclusion against its having belonged to a 

 similarly modified species of Chelone. 



I am indebted to Mr. Catt, of Brighton, for the specimens of the right scapula and 

 coracoid, in almost their natural juxta-position, PI. 48, fig. 9, of a Turtle which must 

 have been about two feet in length, from the chalk : the letter a shows the 

 surface contributed hy the scapula to the humeral joint, the letter b that by which it 

 was united with the coracoid : c is the base of the acromial process or clavicle, which 

 has been sent off in the same oblique direction as in the recent Turtles ; d is the 

 beginning of the body of the slender scapula. The coracoid has been rotated, so as 

 to show its scapular surface at b : that which it contributed to the shoulder-joint is 

 shown at a : the long and slender shaft of the coracoid and its very gradual expansion 

 is eminently characteristic of the marine nature of the species to which it belonged. 



In PI. 48, fig. 10, is shown the opposite side of the right coracoid of a Turtle 

 of double the dimensions of that from which the preceding specimens came. It is 

 from the chalk-pit at Burham, so fertile in fine fossils, and forms part of the collection 

 of Mrs. Smith, of Tonbridge Wells. The margin of the articular end is more produced 

 than in the Chelone viydas, and, as in the preceding fossil, the articular surface b for the 

 scapula is relatively less in proportion to that for the humerus a, than in the same recent 

 Turtle : the slender beginning of the shaft of the bone is more compressed, less triedral. 

 I estimate the fossil fragment, by the proportions of that of the Chelone mi/das, to have 

 been part of a coracoid of one foot in length, and calculating the proportions of the 

 carapace by those of the Chelone Benstedi, it must have been about three feet six inches 

 in length in the Turtle from which the coracoid in question came. 



