Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/224

186 and inner aspects, and also a portion of the distal end in front. As regards size, it is about a third longer than fig. 4, and, as will be seen presently, differs from it morphologically. Both bones represent aged individuals, as is well shown by their gnarled appearances. Moreover, relatively, they are stouter than the tibiæ of T. elephantopus and T. ephippium, and come closer in that respect to T. vicina. I conceive that the larger (fig. 3) belonged to T. robusta, and the smaller (fig. 4) to T. Spratti.

The following establishes their proportional greater thickness as compared with certain recent species that I have been enabled to examine:—

Thus it appears that the smallest girth of the shaft in T. robusta is greater than that of the tibia of the more slender T. ephippium, which is 2⋅2 inches longer, and that, whilst the antero-posterior diameter of the femoral articulation is 41 millimetres in T. robusta, it is 38 millimetres in T. ephippium; but their distal articulations are about equal in size.

The tibia of Testudo Spratti has the groove on the astragalocalcaneal aspect deep (Plate VI. fig. 4a), whereas it is barely indicated in T. robusta (Plate V. fig. 3a). There are two prominent muscular tuberosities about midshaft in T. Spratti.

The anterior aspects in both are more concave than appears to be the case in the recent species named above; and there is greater dilatation at the articular surfaces; otherwise they do not appear to present further characters to distinguish them from the tibiæ of recent species and from one another.

The distal half of a left fibula from Zebbug represents a tortoise considerably larger than the owner of the tibia, Plate V. fig. 3, but not apparently of greater dimensions than the individuals to which the large femora and coracoid belonged. The tarsal articular surface is trihedral in outline and somewhat convex, whereas it is even in T. ephippium. There is the usual expansion of the articulation as seen