60 
THE EACES OF THE MASCAEENES. 
The bones of the forearm show similar differences as regards their proportions of 
length and width as the humerus, differences which probably are likewise due to sex. 
The ulna (Plate XXVIII. figs. F & G) is a comparatively straight bone, with its radial 
edge but slightly emarginate ; the radius (Plate XXVIII. fig. E) is quite straight and 
remarkably slender. The ulna of an apparently not quite full-grown male individual 
(fig. F) has a length of 118 millims., and a width of 14 raillims. in its narrowest part; 
that of an adult female (fig. G) shows only a length of 64 millims. and a width of 
11 millims. The longest radius in the collection is 105 millims. long, with a circum- 
ference of 29 millims. Of the carpus and remaining leg -bones nothing has been 
preserved. 
Pelvis (Plate XXVI. fig. C, and Plate XXVIII. fig. A)— In the pelvis the sutures dis- 
appear at an early age ; the most important point of its structure is the great width 
of the symphysial bridge between the obturator foramina, which are comparatively 
narrow. In the majority of the individuals the transverse diameter of this bridge is 
much greater than the vertical, although the latter is increased by the development of 
a lower median crest. In very young individuals (that is, in individuals in which the 
horizontal diameter of the pelvis does not exceed a length of three inches) this charac- 
teristic feature of all flat-headed Tortoises is hidden by the development not only of a 
lower but also of an upper crest. Although the iliac bones are slender, like the 
remainder of the skeleton, yet the longitudinal diameter of the pelvis does not much 
exceed the horizontal one. In other respects, only the ilium shows a decidedly charac- 
teristic form : from its middle, which is considerably constricted, three ridges arise, 
running up towards the extremity of the bone, which thus assumes a conspicuously tri- 
hedral shape, with three nearly equidistant spinous processes. 
The two pelves, of which the following measurements are taken, are nearly perfect ; 
fragments of much larger ones are in the collection. 
milliin. millim. 
Longest inner vertical diameter of pelvis from summit of ilium to symphysis 106 80 
Longest inner horizontal diameter of pelvis 98 84 
Shortest inner horizontal diameter of pelvis (between ilio-pubic prominences) 68 55 
Longest diameter of foramen obturatoriu 26 21 
Width of symphysial bridge 22 18 
Depth of symphysial bridge 22 13 
Least breadth of posterior portion of ossa ischii 49 38 
Length of os ilii 93 70 
Least breadth of os ilii 21 15 
Femur (Plate XXIX. fig. C). — Although a considerable number of specimens of this 
bone have been collected, they are, singularly enough, all of middle or small size, and 
show scarcely any diversity of structure. The shaft is slender, nearly straight, irre- 
gularly subtetrahedral, and about as broad in front as behind. The head has an oval 
form, and is slightly raised above the level of the summit of the larger trochanter, from 
