Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/217

Rh The caudal vertebra (Plate V. fig. 1) has lost the posterior half of the centrum, but is otherwise entire. The anterior zygapophyses and concave centrum and transverse processes (a) are well preserved. The last-named present rugged articular surfaces, indicating that the costæ were not ankylosed. There is a small neural crest. Un- fortunately, in the few skeletons of the large recent tortoises in collections, it is rare to find the caudal vertebræ; so that I have had no means of comparing the above with other allied forms. It clearly, however, belonged to a land Chelonian of gigantic size. It was discovered by me in conjunction with several teeth and bones of the small form of Maltese fossil elephant (E. Falconeri).

The length of the neck, so characteristic of T. elephantopus, and probably of the other Galapagos tortoises, seems to have been also a feature in T. robusta, if we may judge from the lengthened centrum of the cervical here alluded to.

The very large coracoid process of the scapula (Plate V. figs. 2, 2a) is also referred to the Testudo robusta. The border of the distal extremity is wanting, and there is a slight abrasion on the inner border of the glenoid cavity; otherwise it is entire, and in an excellent state of preservation, as, indeed, were the majority of the remains from the Zebbug rock-cavity, owing to their investing matrix having been a firm, tenacious blue marl.

The articulating surface of the scapula (fig. 2 a, b) is triangular; its maximum length is 40 millims, and greatest breadth 45 millims, the glenoid cavity (c) being of about the same dimensions. The body presents the usual contorted and trihedral configuration, expanding at both the articular and distal extremities.

The internal border is sharp, and the external rounded and uneven. The superior surface of the body is also rounded, and thins out internally. The lower aspect (fig. 2) presents a triangular-shaped depression (d) at the distal extremity, bounded by an cuter ridge (e) and an inner ridge (f). The latter forms also the boundary to the concavity (g) on the inner aspect of the bone. This excavation, although not seemingly apparent in T. elephantopus, is present to a small extent in the other Galapagos tortoise (T. vicina). Concerning the relations with Mascarene tortoises I am unable to say any thing.

The dimensions of fig. 2 as compared with the coracoids of Galapagos tortoises are as follows:—