AND AYES OF NORTH AMERICA. 



141 



In. 



Lin. 



3 



1.4 





11.5 



2 



2.5 



8 



fi 



3 



3 



Length of seventh marginal, 



Thiokness of " " posteriorly 



Width of " " below 



"Width of eleventh " above 



Length of " " (median) 



Large portions of many costal bones arc preserved. Those show the ossification to have been more extensive than 

 in the species of Chelono. Their thickness is more uniform than in some species. The capitnla of the ribs are round, 

 and are on gubcylindrio bases. The anterior is peculiar for its flattened form ; on its anterior margin is a broad rugose 

 band, which contracts into a groove on the side of the capitular process. The dermal sutures are quite distinct. The 

 vertebral scuta arc longer than wide, with bracket-shaped lateral sutures, little prolonged at the angles. One of the 

 transverse intervertebral sutures is strongly concave, probably backward. Where the capitulum springs from the 

 Inferior surface of the costal bone, there are usually six, or more, or less, radiating short grooves, pointing towards it 

 as a centre. 



In. Lin. 



Width of costal bone, 1 7.8 



Thickness " "on margin, 3 



Length poster half lateral suture vertebral scute, 2 2 



Width vertebral scute on costal bone (greatest) 2 4 



Large portions of both hyosternal) and both hyposternals are preserved, with fragments of an epi- and xiphisternal. 

 The inguinal margin is strongly curved and thickened ; its median portion is concave, with a sharp margin below. 

 The axillary thinned medially and inwardly, and thickened outwardly. The hyposternals are also thinned towards 

 the hyosternals. The episternal is acuminate posteriorly, and steeply bevelled on the outer margin. The xiphis- 

 ternal is attached as in osteopygis, by a groove on its inner face, embracing the margin of the hyosternal. This 

 groove is, relatively, considerably shorter than in the two species of that genus known. The proportions of the bone 

 are narrower than in them ; the edge is thin, and the surface rises abruptly from it over a thickening which does 

 not appear in either of the before mentioned species. The external sutural process is also moro posterior. The 

 margin of the hyosternals is thinner than in 0. cmarginatus, and they thicken inwardly as well as outwardly ; they 

 only thicken outwardly in O. platylomus. . 



Lin. 

 Width hyosternal, 24,5 



Thiokness inguinal margin hypostornal, 5.8 



Width xiphisternal (cross axis) at end inner hypostornal groove, 19 



Width episternal two inches from proximal end, 14.5 



A perfect femur, and a humerus with the head injured, were procured with the other bones. The former is 

 characterized by its slender shaft, tin; great antero-posterior extent of its united head and great trochanter, and the 

 large transverse extent, of the condyles. In general form it is much more like Chelys than Chclone, though in the 

 points mentioned it exceeds the former. The articular surface of the head is very convex, and is prolonged in a 

 narrow band along the summit of the groat trochanter. The little trochanter stands nearly at right angles to the 

 first. The shaft is sub-round medially. Compared with the femur described under Taphrosphys molops, but which 

 may belong to Propleura augusta, the inner tubercle is not so prominent and acute, and the posterior projections of 

 the condyles are not so strong. The head of the uncertain femur is not projected so far forwards, and is much more 

 convex ; the great trochanter is not continuous with it, hence the articular surface is not prolonged. 



In. 



Length of femur, 



Width of head and trochanter, 



Width of condyles, 

 AMELII. rillLOSO. SOO VOL XIV. 35 



Lin. 



o 

 



22 

 18 



