Ill 



M. 



Length of the cotyloid fossa 0.070 



Length of the postfrontal on the inferior suture 0. 195 



Depth of the postfrontal at the honndary of the orbit 0. 13G 



Thickness of the postfrontal of the lower suture 0.019 



Length of the postfrontal from the orbit (^oblique) 0. 115 



Length of the right quadrate 0. 140 



Width (antero-posterior) 0. 110 



Width of the condyle 0.0G4 



Length of the right pterygoid superiorly 0. 155 



Depth of the right pterygoid at the inner columeUar angle 0. 100 



Leegth (oblique) of the columella 0.085 



Restoration. — Better materials exist for the restoration of this species 

 than is usual in the case of most extinct Testuclinata. The cranium was 

 0°.50, or 24f inches, in length. If the neck and carapace were related to it 

 as in the genus Chelone, the total would be as follows : 



Cranium 24f 



Neck and carapace 1391 



Total, 12.83 feet lC2f 



an extent not far from the expanse of the flippers above given, viz, 11.30 feet. 

 The shortness of the cervical vertebrse indicates that the proportions of the 

 neck were not dissimilar to those of the existing marine genera. The flippers 

 were probably similar to the same ; of the hind limbs, nothing can now be 

 stated. The shortness of most of the ribs, considered in connection with the 

 length of the marginals, is remarkable. Thus, the longest rib measures O^.Sl, 

 or 16 inches; width of lateral marginal beyond apex of rib, 2.25 inches; 

 width of vertebra, 3 inches, which is, however, covered by the expansion of 

 the rib, included in this case in the length, 16 inches; total width of cara- 

 pace at middle, 36^ inches; length of carapace, estimated from cranium, 118 

 inches; or, width, 3 feet i inch; length, 9 feet 10 inches. An outline, twice 

 as long as wide, is justified in measure by the size, especially the lengths, of the 

 marginals, which, if placed end to end, would measure on one side of eleven 

 pieces, if each were as long as the median, S-.O inches X H = 7.8 feet. Some 

 of the posterior raargiijpls are shorter than 8.5 inches, while some of the anterior 

 appear to be longer. The length, 8.5, may then be take.i as an average. 

 But they formed the circumference of an open arc, so the axial length of the 

 carapace should be placed at a lower figure than the above. Tliis proposition 

 may be offsetted by the fact that the marginals were not united to each other, 

 and exhibit no indications of contact. The length of seven feet for tlie cara- 

 pace is not, llioi), too much, and, estimating from the size of the head, is too 



